diff --git a/.gitignore b/.gitignore
index b60507f..4b1d8c2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -30,3 +30,4 @@ phpstan.neon
 testbench.yaml
 /docs
 /coverage
+.env
diff --git a/config/bitunix-api.php b/config/bitunix-api.php
index b9ffe0e..056ba9b 100644
--- a/config/bitunix-api.php
+++ b/config/bitunix-api.php
@@ -1,6 +1,9 @@
 <?php
 
-// config for Msr/LaravelBitunixApi
 return [
 
+    'future_base_uri' => 'https://fapi.bitunix.com/',
+    'api_key' => env('BITUNIX_API_KEY'),
+    'api_secret' => env('BITUNIX_API_SECRET'),
+    'language' => 'en-US',
 ];
diff --git a/examples/ChangeLeverageExample.php b/examples/ChangeLeverageExample.php
new file mode 100644
index 0000000..cc1a38d
--- /dev/null
+++ b/examples/ChangeLeverageExample.php
@@ -0,0 +1,61 @@
+<?php
+
+/**
+ * Example usage of Change Leverage functionality
+ *
+ * This example demonstrates how to use the LaravelBitunixApi package
+ * to change leverage for a trading pair on Bitunix exchange.
+ */
+
+require_once __DIR__.'/../vendor/autoload.php';
+
+use Msr\LaravelBitunixApi\Requests\ChangeLeverageRequestContract;
+
+// Example configuration (in real usage, these would be in your .env file)
+config([
+    'bitunix-api.future_base_uri' => 'https://fapi.bitunix.com/',
+    'bitunix-api.api_key' => 'your-api-key-here',
+    'bitunix-api.api_secret' => 'your-api-secret-here',
+    'bitunix-api.language' => 'en-US',
+]);
+
+try {
+    // Get the API instance
+    $api = app(ChangeLeverageRequestContract::class);
+
+    // Change leverage for BTCUSDT pair
+    $symbol = 'BTCUSDT';
+    $marginCoin = 'USDT';
+    $leverage = 12;
+
+    echo "Changing leverage for {$symbol} to {$leverage}x...\n";
+
+    $response = $api->changeLeverage($symbol, $marginCoin, $leverage);
+
+    // Check response status
+    if ($response->getStatusCode() === 200) {
+        $data = json_decode($response->getBody()->getContents(), true);
+
+        if ($data['code'] === 0) {
+            echo "✅ Leverage changed successfully!\n";
+            echo 'Symbol: '.$data['data'][0]['symbol']."\n";
+            echo 'Margin Coin: '.$data['data'][0]['marginCoin']."\n";
+            echo 'New Leverage: '.$data['data'][0]['leverage']."\n";
+        } else {
+            echo '❌ API Error: '.$data['msg']."\n";
+        }
+    } else {
+        echo '❌ HTTP Error: '.$response->getStatusCode()."\n";
+    }
+
+} catch (Exception $e) {
+    echo '❌ Exception: '.$e->getMessage()."\n";
+}
+
+/**
+ * Environment Variables Required:
+ *
+ * BITUNIX_API_KEY=your-api-key
+ * BITUNIX_API_SECRET=your-api-secret
+ * BITUNIX_LANGUAGE=en-US
+ */
diff --git a/src/LaravelBitunixApi.php b/src/LaravelBitunixApi.php
index 823fc07..eb2fe77 100644
--- a/src/LaravelBitunixApi.php
+++ b/src/LaravelBitunixApi.php
@@ -2,4 +2,62 @@
 
 namespace Msr\LaravelBitunixApi;
 
-class LaravelBitunixApi {}
+use GuzzleHttp\Client;
+use Msr\LaravelBitunixApi\Requests\ChangeLeverageRequestContract;
+use Msr\LaravelBitunixApi\Requests\FutureKLineRequestContract;
+use Msr\LaravelBitunixApi\Requests\Header;
+use Psr\Http\Message\ResponseInterface;
+
+class LaravelBitunixApi implements ChangeLeverageRequestContract, FutureKLineRequestContract
+{
+    private Client $publicFutureClient;
+
+    public function __construct()
+    {
+        $this->publicFutureClient = new Client([
+            'base_uri' => config('bitunix-api.future_base_uri').'/api/v1/futures/market/',
+        ]);
+    }
+
+    protected function getPrivateFutureClient(array $queryParams = [], array $body = []): Client
+    {
+        $bodyString = json_encode($body);
+        $headers = Header::generateHeaders($queryParams, $bodyString);
+
+        return new Client([
+            'base_uri' => config('bitunix-api.future_base_uri').'/api/v1/futures/',
+            'headers' => $headers,
+        ]);
+    }
+
+    public function getFutureKline(string $symbol, string $interval, int $limit = 100, ?int $startTime = null, ?int $endTime = null, string $type = 'LAST_PRICE'): ResponseInterface
+    {
+        $response = $this->publicFutureClient->get('kline', [
+            'query' => [
+                'symbol' => $symbol,
+                'interval' => $interval,
+                'limit' => $limit,
+                'startTime' => $startTime,
+                'endTime' => $endTime,
+                'type' => $type,
+            ],
+        ]);
+
+        return $response;
+    }
+
+    public function changeLeverage(string $symbol, string $marginCoin, int $leverage): ResponseInterface
+    {
+        $body = [
+            'symbol' => $symbol,
+            'marginCoin' => $marginCoin,
+            'leverage' => $leverage,
+        ];
+
+        $response = $this->getPrivateFutureClient([], $body)->post('account/change_leverage', [
+            'json' => $body,
+        ]);
+
+        return $response;
+    }
+}
diff --git a/src/LaravelBitunixApiServiceProvider.php b/src/LaravelBitunixApiServiceProvider.php
index c30e13b..589a68b 100644
--- a/src/LaravelBitunixApiServiceProvider.php
+++ b/src/LaravelBitunixApiServiceProvider.php
@@ -2,9 +2,11 @@
 
 namespace Msr\LaravelBitunixApi;
 
+use Msr\LaravelBitunixApi\Commands\LaravelBitunixApiCommand;
+use Msr\LaravelBitunixApi\Requests\ChangeLeverageRequestContract;
+use Msr\LaravelBitunixApi\Requests\FutureKLineRequestContract;
 use Spatie\LaravelPackageTools\Package;
 use Spatie\LaravelPackageTools\PackageServiceProvider;
-use Msr\LaravelBitunixApi\Commands\LaravelBitunixApiCommand;
 
 class LaravelBitunixApiServiceProvider extends PackageServiceProvider
 {
@@ -22,4 +24,12 @@ class LaravelBitunixApiServiceProvider extends PackageServiceProvider
             ->hasMigration('create_laravel_bitunix_api_table')
             ->hasCommand(LaravelBitunixApiCommand::class);
     }
+
+    public function packageRegistered(): void
+    {
+        parent::packageRegistered();
+
+        $this->app->bind(FutureKLineRequestContract::class, LaravelBitunixApi::class);
+        $this->app->bind(ChangeLeverageRequestContract::class, LaravelBitunixApi::class);
+    }
 }
diff --git a/src/Requests/ChangeLeverageRequestContract.php b/src/Requests/ChangeLeverageRequestContract.php
new file mode 100644
index 0000000..034b3ab
--- /dev/null
+++ b/src/Requests/ChangeLeverageRequestContract.php
@@ -0,0 +1,17 @@
+<?php
+
+namespace Msr\LaravelBitunixApi\Requests;
+
+use Psr\Http\Message\ResponseInterface;
+
+interface ChangeLeverageRequestContract
+{
+    /**
+     * Change leverage for a trading pair
+     *
+     * @param  string  $symbol  Trading pair (e.g., 'BTCUSDT')
+     * @param  string  $marginCoin  Margin coin (e.g., 'USDT')
+     * @param  int  $leverage  Leverage value
+     */
+    public function changeLeverage(string $symbol, string $marginCoin, int $leverage): ResponseInterface;
+}
diff --git a/src/Requests/FutureKLineRequestContract.php b/src/Requests/FutureKLineRequestContract.php
new file mode 100644
index 0000000..d0654cc
--- /dev/null
+++ b/src/Requests/FutureKLineRequestContract.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace Msr\LaravelBitunixApi\Requests;
+
+use Psr\Http\Message\ResponseInterface;
+
+interface FutureKLineRequestContract
+{
+    /**
+     * @return ResponseInterface
+     *
+     * interval could be: 1m 5m 15m 30m 1h 2h 4h 6h 8h 12h 1d 3d 1w 1M
+     * limit: max is 200
+     * startTime : milliseconds format
+     * endTime : milliseconds format
+     * type could be: LAST_PRICE, MARK_PRICE
+     */
+    public function getFutureKline(string $symbol,
+        string $interval,
+        int $limit = 100,
+        ?int $startTime = null,
+        ?int $endTime = null,
+        string $type = 'LAST_PRICE'): ResponseInterface;
+}
diff --git a/src/Requests/Header.php b/src/Requests/Header.php
new file mode 100644
index 0000000..2192635
--- /dev/null
+++ b/src/Requests/Header.php
@@ -0,0 +1,110 @@
+<?php
+
+namespace Msr\LaravelBitunixApi\Requests;
+
+class Header
+{
+    /**
+     * Sort query parameters in ascending ASCII order by Key
+     */
+    public static function sortQueryParameters(array $parameters): array
+    {
+        if (empty($parameters)) {
+            return [];
+        }
+
+        ksort($parameters, SORT_STRING);
+
+        return $parameters;
+    }
+
+    /**
+     * Convert sorted parameters to string format
+     * Example: ["id" => "1", "uid" => "200"] becomes "id1uid200"
+     */
+    public static function digestQueryParameters(array $parameters): string
+    {
+        if (empty($parameters)) {
+            return '';
+        }
+
+        $sortedParameters = self::sortQueryParameters($parameters);
+        $result = '';
+
+        foreach ($sortedParameters as $key => $value) {
+            $result .= $key.$value;
+        }
+
+        return $result;
+    }
+
+    /**
+     * Generate a random 32-bit nonce string
+     */
+    public static function generateNonce(): string
+    {
+        return bin2hex(random_bytes(16)); // 32 characters
+    }
+
+    /**
+     * Generate current timestamp in milliseconds
+     */
+    public static function generateTimestamp(): string
+    {
+        return (string) round(microtime(true) * 1000);
+    }
+
+    /**
+     * Generate signature according to Bitunix API documentation
+     *
+     * Steps:
+     * 1. Sort all queryParams in ascending ASCII order by Key
+     * 2. Remove all spaces from body string
+     * 3. Create digest: SHA256(nonce + timestamp + api-key + queryParams + body)
+     * 4. Create sign: SHA256(digest + secretKey)
+     */
+    public static function generateSignValue(array $queryParams = [], string $body = '', string $nonce = '', string $timestamp = ''): string
+    {
+        $apiKey = config('bitunix-api.api_key');
+        $apiSecret = config('bitunix-api.api_secret');
+
+        if (empty($apiKey) || empty($apiSecret)) {
+            throw new \InvalidArgumentException('API key and secret must be configured');
+        }
+
+        // Step 1: Sort query parameters in ascending ASCII order
+        $queryParamsString = self::digestQueryParameters($queryParams);
+
+        // Step 2: Remove all spaces from body (already done if JSON encoded properly)
+        $bodyString = trim($body);
+
+        // Step 3: Create digest: SHA256(nonce + timestamp + api-key + queryParams + body)
+        $digestInput = $nonce.$timestamp.$apiKey.$queryParamsString.$bodyString;
+        $digest = hash('sha256', $digestInput);
+
+        // Step 4: Create sign: SHA256(digest + secretKey)
+        $signInput = $digest.$apiSecret;
+        $sign = hash('sha256', $signInput);
+
+        return $sign;
+    }
+
+    /**
+     * Generate complete headers for authenticated requests
+     */
+    public static function generateHeaders(array $queryParams = [], string $body = ''): array
+    {
+        $nonce = self::generateNonce();
+        $timestamp = self::generateTimestamp();
+        $sign = self::generateSignValue($queryParams, $body, $nonce, $timestamp);
+
+        return [
+            'api-key' => config('bitunix-api.api_key'),
+            'sign' => $sign,
+            'nonce' => $nonce,
+            'timestamp' => $timestamp,
+            'language' => config('bitunix-api.language', 'en-US'),
+            'Content-Type' => 'application/json',
+        ];
+    }
+}
diff --git a/tests/AuthHeaderTest.php b/tests/AuthHeaderTest.php
new file mode 100644
index 0000000..3f39327
--- /dev/null
+++ b/tests/AuthHeaderTest.php
@@ -0,0 +1,48 @@
+<?php
+
+use Msr\LaravelBitunixApi\Requests\Header;
+
+it('sort query parameters', function () {
+
+    $emptyQuery = Header::sortQueryParameters([]);
+    expect($emptyQuery)->toBeEmpty();
+
+    $params = [
+        'z_index' => 'z value',
+        'a_index' => 'a value',
+        'b_index' => 'b value',
+    ];
+    $sortedParams = Header::sortQueryParameters($params);
+    expect($sortedParams)
+        ->toMatchArray([
+            'a_index' => 'a value',
+            'b_index' => 'b value',
+            'z_index' => 'z value',
+        ]);
+});
+
+it('get sorted query params as string value', function () {
+
+    $digestedParam = Header::digestQueryParameters([]);
+    expect($digestedParam)->toBeNull();
+
+    $params = [
+        'z_index' => 'z_value',
+        'a_index' => 'a_value',
+        'b_index' => 'b_value',
+    ];
+    $sortedParams = Header::digestQueryParameters($params);
+    expect($sortedParams)->toEqual('a_indexa_valueb_indexb_valuez_indexz_value');
+});
+
+it('get some random string 32 bit', function () {
+
+    $firstRandom = Header::generateNonce();
+    $secondRandom = Header::generateNonce();
+
+    expect($firstRandom)
+        ->toBeString()
+        ->toHaveLength(32)
+        ->not()->toEqual($secondRandom)
+        ->not()->toBeNull();
+});
diff --git a/tests/ChangeLeverageTest.php b/tests/ChangeLeverageTest.php
new file mode 100644
index 0000000..4db10c8
--- /dev/null
+++ b/tests/ChangeLeverageTest.php
@@ -0,0 +1,20 @@
+<?php
+
+use Msr\LaravelBitunixApi\Requests\ChangeLeverageRequestContract;
+
+it('can change leverage successfully', function () {
+    $api = app(ChangeLeverageRequestContract::class);
+    // This test will make a real API call if credentials are valid
+    // For testing purposes, we'll just verify the method exists and can be called
+    expect(fn () => $api->changeLeverage('BTCUSDT', 'USDT', 12))
+        ->not->toThrow(Exception::class);
+});
+
+it('validates required parameters for change leverage', function () {
+    $api = app(ChangeLeverageRequestContract::class);
+
+    expect(fn () => $api->changeLeverage('BTCUSDT', 'USDT', 10))
+        ->not->toThrow(Exception::class)
+        ->and(fn () => $api->changeLeverage('BTCUSDT', 'USDT', 0))
+        ->not->toThrow(Exception::class);
+});
diff --git a/tests/ExampleTest.php b/tests/ExampleTest.php
deleted file mode 100644
index 5d36321..0000000
--- a/tests/ExampleTest.php
+++ /dev/null
@@ -1,5 +0,0 @@
-<?php
-
-it('can test', function () {
-    expect(true)->toBeTrue();
-});
diff --git a/tests/HeaderTest.php b/tests/HeaderTest.php
new file mode 100644
index 0000000..161798f
--- /dev/null
+++ b/tests/HeaderTest.php
@@ -0,0 +1,135 @@
+<?php
+
+use Msr\LaravelBitunixApi\Requests\Header;
+
+beforeEach(function () {
+    config([
+        'bitunix-api.api_key' => 'test-api-key',
+        'bitunix-api.api_secret' => 'test-secret-key',
+        'bitunix-api.language' => 'en-US',
+    ]);
+});
+
+it('can sort query parameters in ascending ASCII order', function () {
+    $parameters = [
+        'uid' => '200',
+        'id' => '1',
+        'name' => 'test',
+    ];
+
+    $sorted = Header::sortQueryParameters($parameters);
+
+    expect(array_keys($sorted))->toBe(['id', 'name', 'uid']);
+    expect($sorted)->toBe([
+        'id' => '1',
+        'name' => 'test',
+        'uid' => '200',
+    ]);
+});
+
+it('can digest query parameters to string format', function () {
+    $parameters = [
+        'id' => '1',
+        'uid' => '200',
+    ];
+
+    $result = Header::digestQueryParameters($parameters);
+
+    expect($result)->toBe('id1uid200');
+});
+
+it('can generate a valid nonce', function () {
+    $nonce = Header::generateNonce();
+
+    expect($nonce)
+        ->toBeString()
+        ->toHaveLength(32)
+        ->toMatch('/^[a-f0-9]+$/');
+});
+
+it('can generate timestamp in milliseconds', function () {
+    $timestamp = Header::generateTimestamp();
+
+    expect($timestamp)
+        ->toBeString()
+        ->toMatch('/^\d{13}$/'); // 13 digits for milliseconds
+});
+
+it('can generate signature according to Bitunix documentation', function () {
+    $nonce = '123456';
+    $timestamp = '20241120123045';
+    $queryParams = ['id' => '1', 'uid' => '200'];
+    $body = '{"uid":"2899","arr":[{"id":1,"name":"maple"},{"id":2,"name":"lily"}]}';
+
+    $sign = Header::generateSignValue($queryParams, $body, $nonce, $timestamp);
+
+    expect($sign)
+        ->toBeString()
+        ->toHaveLength(64) // SHA256 hex length
+        ->toMatch('/^[a-f0-9]+$/');
+});
+
+it('can generate complete headers for authenticated requests', function () {
+    $queryParams = ['symbol' => 'BTCUSDT'];
+    $body = '{"symbol":"BTCUSDT","marginCoin":"USDT","leverage":12}';
+
+    $headers = Header::generateHeaders($queryParams, $body);
+
+    expect($headers)
+        ->toHaveKeys(['api-key', 'sign', 'nonce', 'timestamp', 'language', 'Content-Type'])
+        ->and($headers['api-key'])->toBe('test-api-key')
+        ->and($headers['sign'])->toBeString()
+        ->and($headers['nonce'])->toBeString()
+        ->and($headers['timestamp'])->toBeString()
+        ->and($headers['language'])->toBe('en-US')
+        ->and($headers['Content-Type'])->toBe('application/json');
+});
+
+it('throws exception when API credentials are missing', function () {
+    config([
+        'bitunix-api.api_key' => '',
+        'bitunix-api.api_secret' => '',
+    ]);
+
+    expect(fn () => Header::generateSignValue([], '', 'nonce', 'timestamp'))
+        ->toThrow(InvalidArgumentException::class, 'API key and secret must be configured');
+});
+
+it('handles empty query parameters correctly', function () {
+    $result = Header::digestQueryParameters([]);
+
+    expect($result)->toBe('');
+});
+
+it('handles empty body correctly', function () {
+    $nonce = '123456';
+    $timestamp = '20241120123045';
+
+    $sign = Header::generateSignValue([], '', $nonce, $timestamp);
+
+    expect($sign)
+        ->toBeString()
+        ->toHaveLength(64);
+});
+
+it('generates consistent signature for same inputs', function () {
+    $nonce = '123456';
+    $timestamp = '20241120123045';
+    $queryParams = ['id' => '1'];
+    $body = '{"test":"value"}';
+
+    $sign1 = Header::generateSignValue($queryParams, $body, $nonce, $timestamp);
+    $sign2 = Header::generateSignValue($queryParams, $body, $nonce, $timestamp);
+
+    expect($sign1)->toBe($sign2);
+});
+
+it('generates different signatures for different inputs', function () {
+    $nonce = '123456';
+    $timestamp = '20241120123045';
+
+    $sign1 = Header::generateSignValue(['id' => '1'], '{"test":"value1"}', $nonce, $timestamp);
+    $sign2 = Header::generateSignValue(['id' => '2'], '{"test":"value2"}', $nonce, $timestamp);
+
+    expect($sign1)->not->toBe($sign2);
+});
diff --git a/tests/KLineTest.php b/tests/KLineTest.php
new file mode 100644
index 0000000..217d342
--- /dev/null
+++ b/tests/KLineTest.php
@@ -0,0 +1,13 @@
+<?php
+
+use Msr\LaravelBitunixApi\Requests\FutureKLineRequestContract;
+
+it('check kline request response code', function () {
+
+    $bootedClass = app(FutureKLineRequestContract::class);
+    $response = $bootedClass->getFutureKline('BTCUSDT', '1h', 100, now()->subHours(6)->milliseconds, now()->milliseconds);
+    expect($response->getStatusCode())
+        ->toBe(200)
+        ->and(json_decode($response->getBody()->getContents()))
+        ->toHaveKeys(['code', 'data', 'msg']);
+});
diff --git a/tests/TestCase.php b/tests/TestCase.php
index 6e766a1..11a3486 100644
--- a/tests/TestCase.php
+++ b/tests/TestCase.php
@@ -3,8 +3,8 @@
 namespace Msr\LaravelBitunixApi\Tests;
 
 use Illuminate\Database\Eloquent\Factories\Factory;
-use Orchestra\Testbench\TestCase as Orchestra;
 use Msr\LaravelBitunixApi\LaravelBitunixApiServiceProvider;
+use Orchestra\Testbench\TestCase as Orchestra;
 
 class TestCase extends Orchestra
 {