What is the right course of action here?

Your answer is fully correct. The sign shown here is a "Yield" sign with an additional plate indicating a priority road layout, where priority comes from the right.

According to German traffic rules, at this intersection:

- The motorbike on the right has the right of way before the yellow car because vehicles coming from the right have priority.

- You, as the driver going straight ahead, also may proceed ahead of the yellow car because it is coming from your left, and you have priority over it.

So, both you and the motorbike can proceed before the yellow car. The yellow car must wait and yield to both of you.

Remember: On intersections without traffic lights, vehicles approaching from the right have priority unless otherwise signposted. The yield sign confirms that you must give way to traffic from your right (the motorbike) and also to the yellow car which is turning into the main road from your left. However, the yellow car must wait because it doesn’t have priority under the specific layout shown here.