What must you anticipate here?

You answered correctly. On German highways, you must anticipate that the driver of a large vehicle like a truck may not notice the beginning of a traffic jam (tailback) in time, especially due to their limited field of view or distraction. Additionally, it is common for motorcyclists to move between lanes of slow or stopped vehicles, particularly in congestion. Both situations require heightened attention and readiness to react: stay alert for sudden braking or evasive actions from trucks, and always check mirrors carefully for motorcycles that may approach from behind or between lanes. Being aware of these potential hazards helps you respond safely and avoid accidents in heavy or changing traffic conditions.