You are driving on the autobahn. What is the correct thing to do in this situation?

Your answer is correct. In heavy fog on the autobahn, you are required to adapt your driving to the limited visibility. If visibility drops below 50 meters, German traffic rules dictate that you must reduce your speed to a maximum of 50 km/h—even if a higher speed limit is posted. Additionally, the rear fog lights should only be used when visibility is less than 50 meters, which helps other drivers see your vehicle from behind. Always remember: the posted speed limit is the maximum allowed under ideal conditions, but you must reduce your speed in poor visibility to ensure safety and compliance with the law. This is known in Germany as "Fahren auf Sicht"—driving so you can stop within the distance you can see clearly.