What is true here regarding the distance between you and the vehicle ahead?

Your answer is fully correct because both points 1 and 2 describe important rules about maintaining safe distance and behavior in this traffic situation.

Point 1 explains that keeping a reasonable truck distance is important because the yellow car behind could pull back into your lane at any time. This means you must leave enough space to react safely and avoid a collision.

Point 2 states that once the yellow car re-enters your lane, it is required to "restore" or keep the distance properly again. This means that the car must maintain a safe following distance and not simply cut in closely.

Point 3 is incorrect because the length of the truck compared to your vehicle doesn’t determine whether the distance is too large or not. The key factor is the safe space to allow for unexpected lane changes or braking — not the physical length of the vehicle ahead.

In summary, German traffic rules emphasize keeping a safe distance to allow for safe maneuvers and to accommodate the behavior of other vehicles, especially when cars merge back into your lane. This prevents accidents and promotes smooth traffic flow. Your answer shows you understand this well.