Floor plan single-family house city villa approx. 240m² without basement

I basically agree with you, but there is no 50sqm storage space anywhere near. In the storage room, a small workbench is also planned plus space for garden tools

Sorry, but garden tools belong in a garden shed. Even the luxury version of that will be significantly cheaper than the built storage room. I would plan a double carport and add the storage room to the living area.... It will be cheaper and you will have more usefully usable living space. (Note: However, we have a basement that, of course, also serves as storage. But garden tools are not found there)

And the living, dining, and kitchen area is large enough for us; the question is how a corner bench/stove/fireplace could potentially fit well

Unfortunately, the room layout is not very suitable for a corner bench with a dining table. How is the stove/fireplace supposed to be designed? You have already mentioned the issue with the upper floor and the chimney shaft.

Doesn't that become problematic and expensive anyway if the technical room is located behind the brick garage? And the pipes have to be routed under a floor slab I still remember that my general contractor urgently recommended that I place the technical room at the front....

The room layout is unfortunately not very suitable for a corner bench with dining table. How is the stove/fireplace supposed to be executed? You've already pointed out the problem with the upper floor and the chimney shaft.

Yes, it isn’t, also because it wasn’t prioritized from the beginning. It’s an issue again now... Execution of the stove is still open, was basically thought to be quite simple like, for example, Nordpeis Capri.

Won't it be problematic and expensive anyway if the technical room is located behind the masonry garage? And the lines have to be routed under a floor slab
I still remember that my general contractor urgently recommended placing the technical room at the front...

That will be about 2-3k additional costs, so bearable

Tell me... has anything changed with your price ceiling?
If my tired eyes don’t deceive me, then in April this year you still started your plans with relatively reasonable interest rates of 2% and an absolute limit of 800,000 EUR.

Now, 8 months later, interest rates have found a floor at around 3.5% (15-year fixed rate), prices have literally exploded over the course of the year (tiles alone cost about 50% more than at the beginning of 2022)...

And in your floor plan, I see tiles everywhere... certainly not for 35 EUR/m²?
Parquet... certainly not under 50 EUR/m²...
Material prices!

Can you manage with 3,000 EUR/m²? That would already be a proud 600,000 for 200m², plus garage, plus storage room, plus incidental building costs, plus kitchen, plus outdoor facilities for an impressive 1,100m²...

As a Town & Country builder, I am generally optimistic, but even that seems pretty tight to me...