What do you do when you see this traffic sign?

Your answer is correct.

This traffic sign indicates an upcoming uncontrolled intersection where all directions have equal priority and no traffic lights or priority signs are present. According to German traffic rules, when you see this sign, you must reduce your speed and be ready to brake because you have to prepare for possible right-of-way conflicts. You cannot rely solely on observing traffic from the right; you need to pay attention to all directions and be cautious. Reducing speed and being ready to stop help prevent accidents in these uncertain priority situations.