What is the right course of action?

In this intersection situation, you must yield to the blue car because it is coming from your right side. The "right-before-left" rule applies at intersections without traffic signs or signals in Germany, meaning vehicles on your right have priority. The blue car, therefore, goes first. You correctly selected to allow the blue car to turn. The motorcycle, coming from your left, has to yield to you, so you do not need to let it go first. Remember: at uncontrolled intersections, always check to your right and give way to vehicles approaching from there.