What is the right course of action here?

In this scenario, there are multiple traffic participants. According to German traffic rules, when approaching an intersection:

1. If there is a cyclist on your left, they have the right of way. This means you must allow the cyclist to pass.
2. The red car, if turning left, typically has to yield to oncoming traffic and other vehicles unless signaled otherwise.
3. If there are no signals or signs indicating otherwise, the vehicle on the main road may proceed first.

It's important to recognize the interaction between vehicles and cyclists, applying the appropriate rules for yielding and right of way to ensure safety. In this case, acknowledging the cyclist's presence is crucial for compliance with traffic regulations.