Single-family house of 200m² in 45° angled construction

I would remove the angle. Then many rooms will have a better layout. What are the two basement rooms with the large light wells used for

I see it the same way. And as so often, these drafts are not cost-optimized. When a plan is priced, it is usual that those asked only price what they see and leave out what they don’t see. The first bearer of the "bad news" (it will be more expensive) usually falls out of the running for the contract too often. From this mechanism and a sense of current construction prices, I also think that the costs will be significantly six-figure above the currently discussed amounts. So what – if it remains affordable for the builders? I know people who have gone far six-figures beyond the initial calculations and don’t regret it a bit.

The polygonal surfaces on the ground floor and upper floor are interesting and can be used sensibly or simply create space to breathe – downstairs a dining area can extend into this space, upstairs a nice communal play area for the children will emerge.

90° angles or not – the builders have to like it, it shouldn’t upset the neighbors too much, because a hostile neighborhood is poison for a good quality of life. I think the slight bend fits well with the plot.

What I would still think further about is:

[*
the stair area, which seems too narrow to me in relation to the otherwise generous size of the house
[*]the expected "quietness" in the study – how is that practicable in summer with a child and garden?
[*]building with age-appropriateness or not – the former would have a few more consequences
[*]does a bedroom facing the "noisy" street work?
[*]How do we live with
[LIST]
[*]toddlers
[*]teenagers
[*]adult nesters
[*]working from home
[*]social life and guests

I find the floor plan interesting. But the master bedroom definitely has more potential. Bed to the right, door to the left .... try some variations

Then I would combine the 45° with the garage into a "Y" right away.

Search tip, where in my opinion (for a bungalow) it is really skillfully done:
-> Rainer Roth Project VSB

Floor plan there on slide 4. I especially like the integration of the garage to the entrance and the access via the corridor at the bend. The plot there is similar.

The property on the Schöner Wohnen site, "Family bungalow with airy floor plan," is presented a bit more tightly.