The vehicle may be stuck in some sort of limp mode or “safety” mode. BMW was the first to implement this feature in case there’s a mechanical issue with the car in which it will limit the power and speed, forcing consumers to take it to the dealership immediately. You may need a special tool or scanner to remove the fault code. I would call a local european specialist on this one. This generation of 7 series is not exactly the best when it comes to repair.