What does this traffic sign indicate?

You are correct! This sign indicates a prohibition for vehicles that are wider than 2 meters including their load. In Germany, a round sign with a red border and a number followed by "m" in the center is a width restriction. This means you cannot enter with any vehicle (including its cargo) if it exceeds the specified width. The purpose is to prevent oversized vehicles from entering areas that are too narrow, such as tunnels, bridges, or streets with limited clearance. It does not indicate the width of the road or a required distance to keep from other vehicles. Remember, always check your vehicle’s total width before entering such restricted zones.