Semi-detached house 130 sqm - This is how it will look

So we had our first meeting with the architect and we came to the following conclusion

Unfortunately, we have a setback on the ground floor where we are not allowed to build on. This was only told to us during the meeting, after we had signed!
What is it called when you are not allowed to build there because something else from the neighboring property lies there?

We thought that maybe we could extend this on the upper floor and thus have a small roof in the garden..
Or is this not allowed..?

What's it about?
New build or used property?
Which offset is meant?
If necessary, upload original plans.
Also with site plan, plot, orientation.
What is your question?
And then fill out the questionnaire!

What do you call it when you are not allowed to build there because something else from the neighboring property is located there?

1. Baulast 2. Easement or both

Or is this not allowed..?

In case 1, this is not allowed; in case 2, one would have to know the registration approval recorded in the land register. For further information, the official site plan and the development plan would be helpful.

Hoihoi...
so you're right... a few pieces of information are missing^^

So it will be a new building.

There is nothing important in the development plan...
Would construction be possible above based on a special permit?
Has anyone had experience?

I also find your post confusing. Did you mean to say that you have to give up your rectangular floor plan and leave out this top left corner because you are not allowed to build there? I also don't understand exactly what the question is.

Would construction be possible there based on a special permit?

No.

Anyone have experience?

Yes. The easement encumbers your property. It precisely ensures that nothing may be built there, not even on the upper floor. In the case of a setback easement, underground construction might still be possible. If the neighbors have no windows in the wall facing your property, or there are only rooms whose lighting is not that significant, such as a bathroom or kitchen, it might be possible to waive the corner in your floor plan by way of deviation according to §69 Building Code NRW, including on the ground floor. Presumably, the planner has already checked that. You should have bought the other half if it bothers you that much.