The seat belt for the front passenger in your car is faulty. What is the right behaviour?

Your answer is correct. If the front passenger seat belt is faulty, it must be repaired before anyone sits in that seat. It is not permitted to let anyone ride there without a functioning seat belt, as seat belts are legally required for all occupants. Adjusting the belt height is not relevant when the belt itself is defective. This rule ensures the safety of all vehicle occupants and compliance with legal requirements in Germany. Always ensure all seat belts are in proper working order before allowing passengers in your vehicle.