Normally you have a key locking handle with which you can disable the turn function for safety reasons usually blocks of apartments, your handle I see does not have a key so what I suggest is open the handle 90 degrees to tilt but leave the window pushed closed, don't let it tilt, next remove the handle completely and return it backwards 90 degrees so its pointing down, then refit the handle or at least just push it on and then see if you can turn the handle again 90 degrees, this will determine if the handle only operates to 90 degrees or the mechanism is a tilt only mechanism