What should you do now?

Your answer is correct because in this situation, reducing speed and maintaining your position behind the red vehicle is the safest and most appropriate action. According to German traffic rules, when approaching slower traffic ahead, you should adjust your speed to keep a safe following distance and only overtake if it is clearly safe and allowed. Driving quickly past the vehicle without sufficient space or clear conditions can be dangerous and is typically not recommended. Staying behind ensures controlled driving, good visibility, and allows you to react to any changes in traffic smoothly.