What is the right behaviour now?

You answered correctly. In this situation, when a faster vehicle such as a motorcycle approaches from behind on a rural road, German traffic rules require you to facilitate a safe overtaking maneuver. This means you should reduce your speed if necessary and drive as far right as is safely possible within your lane or on the roadway. This gives the overtaking driver more space and increases safety for everyone. However, you should not signal or encourage the motorcyclist to overtake, because this could be misunderstood or lead to a dangerous situation—overtaking is always the responsibility of the overtaking driver. When you see a faster vehicle behind, your correct actions are to slow down if needed and keep right, which matches your selected answers. This helps ensure safe and predictable road behavior for overtaking situations.