What must you be prepared for in this situation?

Your selection 1 and 2 is correct.

In a roadworks area in Germany you must always expect the roadway to be worse than usual: uneven surfaces, gravel, dirt, loose chippings, metal plates, and sudden changes in lane guidance. That’s why reduced speed limits are typically posted and why you should increase your following distance and avoid harsh braking or steering.

You must also expect workers and construction equipment to be on or very close to the roadway. People may step out unexpectedly, vehicles may enter/exit the site slowly, and parts of the lane can be blocked. The rule of thumb is: drive especially defensively, be ready to stop at any time, and follow the temporary markings and barriers, not the “normal” road layout.

Answer 3 (police regulating traffic) is not something you must generally expect just because there are roadworks. Police control is only assumed when you actually see officers or specific signals indicating manual traffic control.