You want to couple up a trailer with ball coupling. What is correct?

You answered correctly. When coupling a trailer with a ball coupling, it is essential that the coupling is securely fastened: the claw must fit tightly around the ball and the locking device must engage, ensuring a safe connection. Additionally, the trailer’s electrical system must be connected so that lights, indicators, and other electrical components function correctly. The jack wheel, however, should be raised and secured before driving, not left down, as it is only used for maneuvering the trailer when it is unhitched. Always check both the mechanical connection and electrical connection before driving with a trailer.