What is the right course of action?

In this situation, the correct actions are to allow both the cyclist to turn and the blue car to pass through.

According to German traffic regulations, when turning at an intersection with cyclists present, drivers must give way to cyclists who have the right of way. Additionally, if the blue car is approaching from the right and has the right of way, you need to allow it to pass.

This combination ensures the safety of all road users and adherence to traffic laws that prioritize cyclists and address right-of-way rules. Understanding these interactions is crucial for safe driving and effective navigation at intersections.