Retaining wall to the neighbor on the boundary

Hello everyone. The following situation arises at our property boundary with the neighbor. Due to the hillside location, there is a height difference of up to 1.43m. According to the Saarland State Building Code, walls and enclosures up to a height of 2m can be built without setback areas and without a permit. However, how does it work if I backfill next to the wall? Am I allowed to do that as well? Or do I then need permission from the neighbor?

First of all, I would discuss it with the neighbor - the best solution pleases both parties. What happens if you fill up behind your wall? In the worst case, you have your garden on a plateau and leave your neighbor with a 1.43m high wall and no privacy screen on their side. Would you like that? Even if it were allowed, it would potentially be very foolish to go through with it against a neighbor without communication. You will probably move in there yourself, and if you are not a passionate troublemaker, your quality of life will greatly benefit from at least a non-toxic neighborhood.

Of course I talk to the owner. The neighboring property is not developed.

Well then, I am curious to see what solution you come up with.

Apparently you have already been working diligently on modeling the terrain. Now you want to add fill to the slope? Even if you were only adding fill on a flat base, you should consider the height difference when securing against overturning.

So far, nothing has been modeled on the site. Therefore, I am considering what would be sensible or feasible.