What is the right course of action now?

In this situation, you correctly selected that you should remain behind the tractor and anticipate that it may turn off the road. According to German traffic rules, when approaching a slow-moving vehicle like a tractor, you must drive with caution and keep a safe following distance. It is common for tractors to slow down or suddenly turn off the road into a field or driveway without much warning, so it's important to be alert to any signs that the tractor might turn.

It is not correct to comply with a tractor driver’s indicator-based prompt to overtake. German law states that responsibility for overtaking safely always remains with the overtaking driver, regardless of signals or gestures from others. You must only overtake when you have a clear view, no oncoming traffic, and it is definitely safe to do so. In this case, you must remain behind the tractor and be vigilant for possible turns. This approach ensures safety for yourself and others on the road.