Why are you required to stop now?

Your answer is correct because in German traffic rules, you must stop when the situation requires it to ensure safety.

Stopping because of the cyclist is important, as cyclists have specific rights and vulnerabilities, so you must not endanger them. Additionally, stopping due to a confusing traffic situation is necessary to avoid accidents; if you cannot clearly see or understand who has the right of way, it is safest to stop and wait until it is clear.

Stopping simply because of the yellow truck alone is not always required unless it relates to the right-of-way rules or an immediate hazard. In this case, the confusion caused by obstructed views and approaching traffic (like the cyclist and the truck) together obligate you to stop.

This teaches the important principle: if visibility is limited or the traffic situation is unclear, always stop and yield to others before proceeding, to ensure safe and responsible driving.