Why are you not allowed to overtake here?

Your answer is correct because in this situation, overtaking is not allowed for two main reasons according to German traffic rules:

1. You do not have a clear and adequate view of the road ahead. The road curves ahead and there are trees and other visual obstacles, so you cannot see if any vehicles, cyclists, or hazards are coming toward you, which makes overtaking dangerous.

2. You cannot maintain a safe passing distance from the cyclists while oncoming traffic might appear. German law requires you to keep enough lateral space when overtaking cyclists to ensure their safety. Since the road is narrow and you might meet vehicles coming from the opposite direction, you cannot safely pass the cyclists without endangering them or oncoming vehicles.

The third option is not fully relevant here because the central lane markings are dashed, which by itself would permit crossing but doesn't override the safety concerns mentioned. So the key reasons are visibility and the inability to maintain vehicle and cyclist safety. This rules help prevent accidents in situations with limited sight and narrow roads.