What is the right course of action?

Your answer is correct because you allow the blue car to turn first. According to German traffic rules, when multiple vehicles approach an intersection without traffic lights, the right-of-way is usually determined by who is on the right or by who is already in the intersection.

Here, you are driving straight ahead, the blue car is turning left, and the motorcycle is coming from the opposite direction. The blue car must be given priority when turning left across your path if there are no other right-of-way signs or signals.

You do not have the right to proceed first because the blue car must complete its turn safely, and the motorcycle has to stop or yield to vehicles turning from its right side unless otherwise indicated.

Hence, allowing the blue car to turn first is the proper course of action to ensure safety and comply with right-of-way rules at this intersection.