Why are you required to stop here?

You are required to stop because of the red car, which has the right of way at the intersection. According to German traffic rules, when you encounter a "Give Way" (Vorfahrt gewähren) sign, you must yield to all vehicles on the priority road before entering the intersection. This includes waiting for any cars approaching from the right or left that have priority. The cyclist and pedestrian do not require you to stop in this specific situation, as the driver's primary obligation is to yield to the cars that have right of way on the road you intend to enter. This rule ensures safe and orderly traffic flow at intersections.