How high does the house rise - how high to pile up earth (cellar depth low)?

Phew!!! Enough has already been said about the (mis)planning, the child has now fallen into the well. I also think that an experienced landscape gardener needs to take care of this, who can get the best out of this tricky situation. The money saved on a lifting system now has to be invested two or three times over in the planning and construction of the terrace and garden. Missing exterior plaster and unnecessary base paint are, in my opinion, the smallest problems here.

In what way do you think something (what exactly?) was overlooked here?

The consequence of what such a number means, for example. And the ten steps up to the front door – did you consider those just a visual relief for the drawing? Then I read here about a lifting system that you wanted to avoid, and that's why you played around with the house height. So basically the thought process goes something like: "Wow, such a thing costs four figures? ... that's expensive ... can't we just leave it out if we raise the house instead?" (Answer: yes, that sounds clever because it "saves" the price of the lifting system on the general contractor’s quote. And once the house is standing, you can try your luck with the lottery, and until the jackpot is hit, we ask the internet for a smart interim solution). This can no longer be convincingly justified by mere amateurism in reading construction drawings. The house overall feels like someone measured the slab one entire meter off in height and realized it too late – after that, they simply finished the house as a cover-up. Such a tiny little difference ;-) can no longer be fudged away with a camouflage marker. Cleverness and skill aside, it now costs money "in one piece" to "heal" the mistake.

At that time, we were glad because all other general contractors we consulted had planned a normal basement that would have gone normally deep into the ground, which would have failed in our case due to the sewage system. [...] The "raising" of the basement was rather a cost saving compared to an originally desired normal-deep basement (which was then not possible).

One can only comment on this in Kölsch: "dat kashmir nit vüürstelle." Apart from the clearly comparatively lower costs of a lifting system here, you do not necessarily have to route the wastewater pipes beneath the slab; a washing machine does not have to be located in the basement by divine decree. The planner must truly have read all volumes (including the anniversary edition!) of the adventures of a cunning East Frisian farmer. This faulty planning really has to be seen – neither Günter Willumeit nor Fips Asmussen could have told this :) The building inspector will probably also need to be convinced with several bottles of Korn that this basement is not a full floor ;-) Dear readers: please do not imitate! – this is a textbook example of an alleged fixation on a house design with subsequent clarification of the plot’s topography. I can hardly make sense of it otherwise.

Yes, we were on site several times, also with the general contractor.
He was the first general contractor who looked at the construction site immediately and was the only one who noticed that the sewage system is not deep in the ground and that we therefore have to raise the basement.

The "raising" of the basement was rather a cost saving compared to an originally desired normally deep basement (which was then not possible).

Man, man, man - I would say the "raising of the basement" was probably the biggest nonsense idea I have ever heard from a general contractor...

No use - house and above-ground basement are standing. Either you make the basement a proper ground floor or the garden and landscaping builder has to fix it reasonably.
Best regards, GD

What kind of opening is that actually under the patio door [Ansicht hinten]?

but not that we would be so much higher than the neighbors-

and thus would come to a level with the neighbors.

The neighboring height really doesn't matter, does it?

For this, I would also have to have unplastered spots plastered on the outside - how long does something like that take?

You have completely different worries. And if you have to have it plastered… or plaster it yourself… that doesn’t matter.

The "raising" of the basement was rather a cost saving compared to an originally desired normally deep basement by us (which then was not possible).

You do realize that with the basement not where it should actually be, with a light shaft for an office room, i.e., below the ground surface, you now have to artificially create a new ground surface?! Your ground floor is where normally the first floor would start. Your basement is where the ground floor should be.
I would put the problems with the plaster last.
What’s important is that you get an adequate barrier-free area from the interior areas to the front door and terrace. However, steps are unavoidable, whether to the garden or front door.
Turn to a landscape gardener - that is the best idea.
In my opinion, all these considerations come a bit too late, the thing is basically done, the cat is out of the bag. Now you just have to somehow deal with it.

The basement itself (built like that) is complete nonsense. At first, I thought it was April 1st.

Just build a pool right away: that doesn’t require any excavation work.