Setback city villa approx. 200m² with southern orientation

600 k with basement in living quality very I do not. I still see all in mind. 700 k

Actually too many wishes for the plot and budget

What is the building envelope

I can only agree with that. 700+, depending on self-discipline, if we mean a ready-to-move-in house including all additional costs and especially the planned basement. Without a basement, even the 500 K will already be a challenge.

How is the building window

This was already defined at the beginning:

Zoning plan/restrictions Size of the plot 460m² (approx. 17.5m wide, 26.5m deep) Slope No Floor area ratio 0.4 Gross floor area ratio 0.8 Building window, building line and boundary 3m to the east, west and north; 6m to the south towards the street

That leaves 11.5 x 17.5 m.

Our problem is the issue with the boundary development of the terrace.

At our place it is allowed and is done like that all the time. You are only not allowed to roof the boundary terrace; there you have to keep a 3m distance. Whether it is allowed for you, you have to find out. I also believe that you could "push" the garage all the way to the back. Then you would have 12 meters of boundary development in total (3 + 9 m). That would allow you an entrance in the east. If the entrance remains in the south, I wouldn’t place it so far in the middle. Rather where the plant is currently marked. Then extend the stair wall down to the south and place the entrance sideways into the dining room. But the staircase is too short at just under 3.5 m anyway; you’d rather need 4 meters – depending on the ceiling height.

The plot has already been purchased. In our area, the market currently offers almost nothing, so you have to be quick. We will definitely manage to get something done there. Regarding the budget, I already said that there isn't really one at the moment. Regardless of that, we want to have a rough plan according to our wishes, then we'll look at the costs. If it ends up being 700k, so be it.

Unfortunately, pushing the garage to the back is not possible - the development plan doesn't allow it. Putting the terrace on the side seems to be possible here as well, but it's not 100% certain yet. The staircase is an issue; we will definitely have it turn 90° at the bottom so that you don't walk directly toward the couch but rather in the direction of the "dance hall". That was really a great tip. It also makes the staircase a bit shorter and fits better. The teenager visits have to pass by us. We discussed it - it's intended that way ;-)

Potentially, we also still have the granny flat in the basement to house teenagers.

We had already considered Würfel's suggestion with the entrance facing the dining room, but came to the conclusion that we don't like that so much. The sightline when entering the room isn't so great then.

Otherwise, I'll browse through here a bit - unfortunately, I have a little time at the moment :(

Thanks for your tips!

That's how it's intended ;-)

Is it intended that you have no privacy on the sofa?

The line of sight when entering the room isn't that great.

What's so great about the line of sight now? That you look at the side wall of a cabinet?
I would work on that. You have to take care of the tall cabinets and the rest of the kitchen furnishings anyway – currently only a kitchenette is shown – your other kitchen furniture is still on the terrace :D
And while you mention it: where does the sightline from the entrance door go? To the cellar stairway door. Is that art or can it go? I would point to the latter :)