Who is required to indicate a change of driving direction here?

In this situation, the rule is that every driver who changes their driving direction must indicate (use their turn signal) to alert others. This applies to you (1), the red car (2), and the motorbike (3), because all are making a turn or changing lanes as shown by the arrows.

According to German traffic rules, signaling is required to ensure safety and predictability on the road. It helps other road users understand your intentions and adjust their driving accordingly. Even when you have right of way, indicating is mandatory when changing direction.

Since all three vehicles are turning, it is correct that all three must signal. This rule helps prevent accidents and confusion in such traffic situations.