Why are you required to stop here?

Your answer is correct because according to German traffic rules, you must yield and, if necessary, stop for any road users who have the right of way at an intersection. In this scenario, the cyclist approaching from the left on the priority road has priority, so you must stop to let them pass safely. The stopping requirement is not because of the green car (which is parked and not threatening), nor the pedestrian (who is on the sidewalk and not crossing at the moment). This rule is based on the general principle of yielding to traffic on the priority road, as indicated by the "Yield" sign (Zeichen 205). Always pay close attention to such signs and the actual traffic to know when a full stop is necessary to avoid collisions.