Hello ximdonexx,
Welcome to the Apple Support Communities. I understand the Xbox Wireless Controller the left and right thumbstick buttons aren't working. I'll be happy to explain.
Most games may not utilize all the functions of the controller and also may not be supported when paired with your iPad. If possible, check a controller-supported game's controls screen (usually in the game's settings) to see if those buttons can be utilized. You can learn more here: Connect a wireless game controller to your Apple device
Take care.