Who can move first in this situation?

Your answer is correct. According to German traffic rules, when entering a main road from a driveway or side path, you must yield to all traffic already on the main road. In this situation, the red car is currently stationary, waiting to enter or cross the main road, and the blue tractor is coming from the opposite direction. Since you are driving on the main road and have no signs indicating you must yield, you have the right of way.

The key rule here is that vehicles already on the main road have priority over those entering from side roads or driveways. Thus, you can move first before the red car or the tractor. Understanding the right of way when merging or crossing roads helps you avoid accidents and ensures smooth traffic flow.