What is the right course of action now?

On German highways (Autobahn), drivers must keep to the right as much as possible unless they are overtaking—this is called the “Rechtsfahrgebot” (keep-right rule). You should only use the middle or left lane if needed to overtake slower vehicles in the right lane or if traffic is too dense to stay on the right. Once you have finished overtaking and the right lane is clear, you must return to the right lane.

In this situation, since the truck lane (right lane) is now available and you are not overtaking, you should move back into the right-hand lane. Remaining unnecessarily in the center or left lane is not allowed and can disrupt traffic flow and create risks for other drivers. Your answer is correct: by moving into the right-hand lane as soon as it is safe, you follow the German traffic rules. Remember this right-hand driving principle for future Autobahn situations.