diff --git a/README.md b/README.md
index 8699254..ccf75b2 100755
--- a/README.md
+++ b/README.md
@@ -89,13 +89,14 @@ foreach ($portfolioResponse->getPayload()->getPositions() as $position) {
 // Пример 3. Создание лимитной заявки
 use Dzhdmitry\TinkoffInvestApi\TinkoffInvest;
 use Dzhdmitry\TinkoffInvestApi\Schema\Request\LimitOrderRequest;
+use Dzhdmitry\TinkoffInvestApi\Schema\Enum\OperationType;
 
 // Создать клиент с токеном
 $client = TinkoffInvest::create('YOUR_TRADE_TOKEN');
-// Сделать запрос на создание лимитной заявки на счете "Тинькофф"
+// Сделать запрос на создание лимитной заявки на счете "Тинькофф" (Заявка на покупку 5 лотов USD по цене 75.20)
 $limitOrderResponse = $client->orders()->postLimitOrder(
     'BBG0013HGFT4', 
-    new LimitOrderRequest(5, 'Buy', 75.20)
+    new LimitOrderRequest(5, OperationType::BUY, 75.20)
 );
 $order = $limitOrderResponse->getPayload();
 
diff --git a/src/TinkoffInvest.php b/src/TinkoffInvest.php
index 7254197..6d23944 100644
--- a/src/TinkoffInvest.php
+++ b/src/TinkoffInvest.php
@@ -8,8 +8,6 @@
 use Dzhdmitry\TinkoffInvestApi\Api\Portfolio;
 use Dzhdmitry\TinkoffInvestApi\Api\Sandbox;
 use Dzhdmitry\TinkoffInvestApi\Api\User;
-use Dzhdmitry\TinkoffInvestApi\Schema\Payload as Types;
-use Dzhdmitry\TinkoffInvestApi\Schema\Response\OrdersResponse;
 use GuzzleHttp\Client;
 
 class TinkoffInvest
@@ -21,6 +19,36 @@ class TinkoffInvest
      */
     private RestClient $client;
 
+    /**
+     * @var Market|null
+     */
+    private ?Market $market = null;
+
+    /**
+     * @var Operations|null
+     */
+    private ?Operations $operations = null;
+
+    /**
+     * @var Orders|null
+     */
+    private ?Orders $orders = null;
+
+    /**
+     * @var Portfolio|null
+     */
+    private ?Portfolio $portfolio = null;
+
+    /**
+     * @var Sandbox|null
+     */
+    private ?Sandbox $sandbox = null;
+
+    /**
+     * @var User|null
+     */
+    private ?User $user = null;
+
     /**
      * @param RestClient $client
      */
@@ -50,7 +78,11 @@ public static function create(string $token): TinkoffInvest
      */
     public function market(): Market
     {
-        return new Market($this->client);
+        if ($this->market === null) {
+            $this->market = new Market($this->client);
+        }
+
+        return $this->market;
     }
 
     /**
@@ -58,7 +90,11 @@ public function market(): Market
      */
     public function operations(): Operations
     {
-        return new Operations($this->client);
+        if ($this->operations === null) {
+            $this->operations = new Operations($this->client);
+        }
+
+        return $this->operations;
     }
 
     /**
@@ -66,7 +102,11 @@ public function operations(): Operations
      */
     public function orders(): Orders
     {
-        return new Orders($this->client);
+        if ($this->orders === null) {
+            $this->orders = new Orders($this->client);
+        }
+
+        return $this->orders;
     }
 
     /**
@@ -74,7 +114,11 @@ public function orders(): Orders
      */
     public function portfolio(): Portfolio
     {
-        return new Portfolio($this->client);
+        if ($this->portfolio === null) {
+            $this->portfolio = new Portfolio($this->client);
+        }
+
+        return $this->portfolio;
     }
 
     /**
@@ -82,7 +126,11 @@ public function portfolio(): Portfolio
      */
     public function sandbox(): Sandbox
     {
-        return new Sandbox($this->client);
+        if ($this->sandbox === null) {
+            $this->sandbox = new Sandbox($this->client);
+        }
+
+        return $this->sandbox;
     }
 
     /**
@@ -90,7 +138,11 @@ public function sandbox(): Sandbox
      */
     public function user(): User
     {
-        return new User($this->client);
+        if ($this->user === null) {
+            $this->user = new User($this->client);
+        }
+
+        return $this->user;
     }
 
     /**