Challenge at a 1/4 circle house ;)

However, I don't understand why the house is being pushed to the west boundary instead of orienting a somewhat narrower, rectangular house on the east side.

The house would only have a depth of 5-6m. As soon as you move back a bit to create more depth, you have to move back a lot because the curve is extremely unfavorable. This would, in turn, narrow the terrace + garden, which the OP does not want. In the end, you almost end up at the first picture from #1. The 3m to the east still have to be accounted for, and 434m² is just 434m².

The house would only have 5-6m depth. As soon as you move something back to create more depth, you have to move back a lot because the curve is so extremely unfavorable. That would, in turn, narrow the terrace + garden, which the OP does not want. In the end, you almost end up with the first picture from #1. The 3m to the east still have to be added and 434m² is just 434m².

By rectangular, it means without a curve: right angles. The L-shape, as you drew it. Or similar.
Doesn’t matter...
O.T.
It slowly seems to be becoming a trend here to keep creating new threads about the same house, where the same things are discussed over and over. Every time it gets uncomfortable for the builder...
was/is also such an artist. Meanwhile, the plot is constantly rotated anew, but the planning is always set the same way instead of breaking away from the knot.

Overall, once again the second step is taken before the first. A house is planned before the requirements are even established.

An [Altenteil] in the upper floor (without an elevator a contradiction in itself) is set as the planning basis without being clear about the purpose/need/advantages and disadvantages, etc.

Then a chain reaction starts: a large building is necessary to fulfill all wishes -> too large for the plot -> the house is pushed to the unfavorable/rounded building boundary -> half of the rooms have to make do with poor compromises -> construction costs explode -> and so on and so forth. FOR NOTHING.

Yes, I am really surprised that someone has already bought a piece of land but still doesn’t know what kind of rooms they actually need or apparently has no concrete ideas about it yet. Did they just buy the land on the side because there happened to be one? Like we used to grab bananas just because there were some?

You have to at least know whether you want no children or three. Whether that will work out, no one can say, but to me, that belongs to the house planning. Whether the parents will also need a room in the house in 20 years, I don’t find that so important for life planning. Of course, there are always special cases and exceptions.

so my surveying office said no, but I think yes

Rule number 1: The surveyor is always right!
Since no other regulations are made in the development plan and the Building Use Ordinance 2013 applies, §19, paragraph 4, sentence 2 applies:
The permissible floor area may be exceeded by up to 50 percent by the floor areas of the facilities referred to in sentence 1, ...

Terraces

... are not mentioned in sentence 1 and therefore count fully.

Basement, floors: 0, 1.5

Two-family house, meaning 120m2 ground floor + 120 first floor

So what now? Two full floors or 1.5 (even if half floors do not exist)? Show the first floor. Show a view (or all four).

I would also like to see the cut... that is enough for me. I am curious about the roof. I do have some ideas, but it would be interesting to see how wants to do it. I also see it as questionable, this "when the old ones get old". The floor plan is not important at all for now!