Plot with slope - New development area

Addendum: I did/would not have noticed whether/that the camera was not held straight.

Because of such funny posts, I usually avoid forums.

That was not a funny post. By straightening the photo, the property is only shown as it actually is.

I also think that the property looks flatter in the photos and in reality.
We had received this plan from the city...

That sounds as if you do not trust the development plan. My correction was only meant to clarify that this mistrust is unwarranted. The slope is significant, as the previous speakers have clearly pointed out. Hence my surprise at your terseness, for example that you do not explain your understanding of a basement in more detail. Anyone who reads the contour lines cannot understand your questions.

Would the additional costs be significantly higher without a basement?

What do you mean by additional costs? Additional compared to what? How are 3m of height difference within the building footprint supposed to be compensated, if not by a floor? Do you call this a basement, or should there be another floor beneath?

You have not filled out the questionnaire. Nobody knows what you want, what you need, and how much money you want to invest.

I wouldn’t have chosen a basement. It makes me think of the townhouses in the UK. Often there is a staircase from the outside going down (about 2 m) into a light well and from the back of the house going up into the garden. Usually with another light well. Some are really nice little terraces, almost like gardens.

Addendum: I did/would not have noticed whether/that the camera was not held straight.

That is exactly what meant: no one can judge anything if pictures are taken with a crooked camera. I say this as a photographer, not to hurt any feelings, but to point out to the OP that his question is misleading with his distorted photos.
And why not put that in some kind of indirect humor?

Because of such funny posts, I usually avoid forums.

Yes, then you urgently need a basement where you can go to laugh. And of all people, to 's rather factual and sober posts. Sorry, I'm having a fit of laughter right now. The OP probably hasn't found a bigger blunder. Seriously, so far we have almost zero information on ideas. No one knows what you need. That's why there is this questionnaire: https://www.hausbau-forum.de/threads/grundrissplanung-unbedingt-vor-Beitrag-Erstellung-lesen.11714/ After that, one can talk about ideas.

Yes, then you urgently need a basement where you can go to laugh.

That also came to my mind with my post, but I refrained because humorless people don’t understand that :P As a frequent writer, I usually don’t reply anymore if the forum rules are not followed: in this case, I recognize that you have not read the pinned posts. If you want to further improve the quality of this thread, you should provide the information.