What is the right course of action?

Your answer is correct because, according to German traffic rules on the Autobahn, overtaking should be done on the left, and after completing the overtaking maneuver, you should return to the right lane to allow faster vehicles to pass. In the scenario, you are supposed to first overtake the slower vehicle (the van) by moving into the left or middle lane, and only after successfully passing it should you move back to the right lane.

Moving immediately to the right lane while still alongside or behind the vehicle is not appropriate, as it can cause dangerous situations or force drivers to slow unexpectedly. Slightly braking to create distance is generally not recommended because it could disrupt traffic flow and may be unsafe at higher speeds.

This principle is part of the "Rechtsfahrgebot," the keep-right rule, which states you should drive on the right lane unless overtaking. After overtaking, it is required to move back to the right lane as soon as it is safe to do so. This maintains smooth traffic flow and reduces congestion on higher-speed lanes.