At these traffic lights with a green arrow sign, where should a vehicle stop before turning right?

Your answer is correct. In Germany, when you see a red traffic light with a green arrow, it means you may turn right, but only after stopping first. The rules specify that you must stop at the stop line if there is one. If there is no stop line, you must stop before the crossing or junction. This ensures that you have a clear view of the traffic and pedestrians crossing before you proceed. You cannot simply turn right without stopping, as that could be dangerous and is not allowed by traffic regulations. Stopping first helps avoid accidents and ensures safety for everyone at the intersection.