Distance from terrace to property boundary

Thank you for your explanation. Exactly that with the backfill (up to 1m? or something like that

This interpretation of the heights is handled differently depending on the region.
For example, the SächsBO says nothing about this.
Some assume 1.5m here, others 2m.
It would have to be researched whether there are administrative instructions in Saxony. I have not found anything on this at short notice, but I also haven't consulted Juris.

It would be easier to assess the situation if the terrace is covered and this covering is attached to the house; then the setback (at least 3m in most cases) must be observed from the end of the covering and not from the house.

I currently do not have time to address the second situation, but I will gladly follow up on it later today if no one else has adequately dealt with the problem by then.

He means he is on the original terrain and therefore would not have to intercept

Basically, the rule is that whoever leaves the original terrain is responsible for the securing, § 909 Building Code. Sometimes this is also explicitly stated again in the development plan.

The same applies to embankments, § 17 Saxon Nuclear Energy Act.

You probably have submission plans at home from your building application; you can quickly see there whether you have left the original terrain course. Alternatively, there should also be the surveyor’s documents. You would have to determine that at the disputed boundary.

In some development plans, there are also height indications; I would also check that. Based on pictures, it is always very difficult to recognize differences in height, etc.

The question in case of doubt is whether you could prove that the neighbor changed the original terrain level and not you.

Thank you for your explanations.

I actually looked at the site plan and the elevation points indicated there actually show a clear direction. From west to east the numbers get smaller... and you can also see live that the other 2 buildings to the west are higher, not so much that you have to catch it, but you can see it. From which documents can I deduce whether the natural course has been altered? Regardless of the above site plan.
But how is it if it is simply the natural course of the terrain?

Thank you!

Your building application must include a height plan and should do so. In case of doubt, there are topographic maps. You must know how deep you have excavated. That looks easily like 1 m in the picture?

Nothing was excavated here. 30cm were removed from the existing ground and replaced with a 30cm sand layer for the base slab. The piles of earth are the excavation for the base slab, the driveway, and the terrace area, which were then backfilled with RC material or gravel sand.

But what if it is simply the natural course of the terrain?

If according to your documents you have not deviated from the natural terrain course, then you do not have to support his property. However, that would mean that he must have filled in to actually create an edge.
Do you know if he has filled in?
Otherwise, you could also view his construction documents at the building authority, where his original and actual terrain should be visible.
As a neighbor, you always have legitimate interest.