Floor plan of a single-family house, 2 floors with basement, approx. 190 m², plot approx. 440 m²

Thank you very much for posting.
I skimmed through it, and it results in a livable house.
Most items are standard, others are of higher quality than average houses. There are also a few necessary construction-side surcharges, which you have factored in.
However: did I overlook the basement? A basement is not mentioned.
And here we come to the price: Your stated house price fits a house on a slab foundation. But not plus basement.

The basement is included in the offer. I am attaching an excerpt from the offer:

which page? which post? I already have blisters on my index finger because I was looking for the plumbing page in the first post :D

It can be found in the second post :D

No, with us the geologist went berserk and then the structural engineer got cold feet. We have a 13 m slope behind the house. Admittedly soil class 5-6 but what can you do. Well, who could have guessed that a Dr. in 2017 would determine that what has naturally grown over millions of years cannot hold.

but there is something about a utility basement and how it is constructed.

Oh wow, 13m is quite a lot :O but still, if it has always held like that...

Well, apparently the structural engineer wanted to sleep well at night :D

Because of the utility cellar or living cellar, the seller explained to me that the only difference is the lighting, ventilation, and fire protection. Otherwise, all the rooms in the cellar have underfloor heating (except, I think, the HAR), etc. Just as stated in the contract.

So I have now had a few other things included, a few floor-to-ceiling windows, the exterior foil coating, the bathroom in the cellar, etc. And the updated offer price is now €360,000. Without the landing staircase but with a normal 2/4 winding staircase, because the landings would cost €6,000 for the two staircases... We are still thinking about that. Better photovoltaics and save the money for the landings.

So the price is still unbeatable. But I talked with two "real" builders on Instagram and both said that it really was like that and there were no additional costs after signing (except for things they really wanted extra afterwards; e.g., one family who took the landing staircases for €6,000). And the houses are already built and the people are more or less satisfied. We are also allowed to visit a family for an inspection on the weekend or next week.

So apparently you could choose a worse general contractor....

But as I said, everything is still open. The others only have appointments in a week. They were a bit slower in scheduling.

So apparently one could choose a worse general contractor....

Yes, but always a better specialist for floor plans than the creator of the design posted here.

Yes, but always a better expert for floor plans than the creator of the design posted here.

Hmm... We ourselves are the creators. So we have also thought about it intensively again in the past few days and we must say, we really like it. But the general contractor, or all general contractors still in the running, also have their own architect(s) and they might have some ideas on how to implement this and that.
But regarding the dilemma that we want the living room on the ground floor and the bedroom and bathroom on the upper floor facing the forest at the back (and accordingly the drains run down the wall of the living room), surely no one will be able to change that... I think or rather hope that it can somehow be cleverly hidden behind furniture.