I use this simple HTTP Post request to post some values on my API from Arduino using Switch. each time I push the switch it send a different values to API.

void switch_led() {
bool SwitchReading = digitalRead(SWITCH);
if (SwitchReading == HIGH) {
Serial.println("Now pressed....");
state = state + 1;
if (state % 2 != 0) {
  digitalWrite(LED, HIGH);
  char data1[] = "{""LDRValue"": 88888888}";
  Serial.println("\nStarting connection to led server...");
  if (client.connect(server, 8040)) {
    Serial.println("connected to post server");
    client.println("POST /api/sensor HTTP/1.1");
    client.println("Host: 192.168.2.116:8040");
    client.println("Content-Type: application/json");
    client.print("Content-Length: ");
    client.println(sizeof(data1));
    client.println();
    client.print(data1);
    Serial.println("1.finish");
  }
  Serial.println("2.finish");
}
else {
  digitalWrite(LED, LOW);
  char data2[] = "{""LDRValue"": 1111111111}";
  Serial.println("\nStarting connection to led server...");
  if (client.connect(server, 8040)) {
    Serial.println("connected to post server");
    client.println("POST /api/sensor HTTP/1.1");
    client.println("Host: 192.168.2.116:8040");
    client.println("Content-Type: application/json");
    client.print("Content-Length: ");
    client.println(sizeof(data2));
    client.println();
    client.print(data2);
    Serial.println("3.finish");
  }
  Serial.println("4.finish");
}
delay(500);
   }
}

It works perfect for the first and second posts in both Arduino and API but at the third post it works fine on Arduino but it takes long time on the API(about 2 minutes to get the post). The fourth and the fifth posts also works fine but the sixth is same as the third. Knowing that my API works 100% with Raspberry Pi and it has no errors.

The same thing for PUT and GET.