Single-family house approx. 180 m² - What do you think about that?

.... and the running around in the dressing room as well as in the kitchen is not exactly well solved.

Even if you think you imagine the house EXACTLY like this, later, when a professional/architect has done a proper planning, you will see what kind of labyrinth you have created. You are now so fascinated by your "ability" to work with the program that you do not recognize the essential: the functionality of the design is something different from ticking off a table of specifications. One is the program you are dealing with, the other is the planning of a house.

Utility room "in" the living room is a serious mistake, 1.2 bathrooms are sufficient for a space-saving terraced house, you don’t really want a bathroom facing south either, and whether "sliding in nature" is so romantic, I doubt it. You don’t have to sugarcoat that either.

As far as I know, the same boundary distance rules apply to basements as to the rest of the building, so the idea of placing the basement right at the boundary won’t work.

Since these are just the first steps, everything is still open.

Utility room "in" the living room is a big blunder, 1.2 toilets are sufficient for a space-saving terraced house, nobody really wants a bathroom in the south either, and whether "schiddern in nature" is so romantic, I doubt.

Somehow Yvonne picked up a new language over the weekend. I don't understand a thing. What do you mean by 1.2 toilets? What is a space-saving terraced house? And what is "schiddern"?

Yes, we are still at the beginning and nothing has been built yet.

Maybe a brief note on our considerations regarding the orientation of the individual rooms:
We see living/dining/cooking in the south or west.
Bathroom with sauna we also see in the south or west to have the sun while using the sauna.
Bedroom in the east to have the sun in the morning and otherwise keep the heat outside.
I think the orientation of the upper floor is not too bad.

What do you think about these considerations?

In general, the land is also owned by the family in the south, so there is no risk of something being built there.

I find the alignment okay. Better tell me why you want to put a basement under the carport instead of the house? And who is supposed to live upstairs later and watch you during the sauna session by the pool? Apartment upstairs later without a balcony? I would remove this partition nonsense from the list.

Why is the floor plan "straight," but the plot "slanted"?

A carport basement hardly saves anything. Several manufacturers of basements (each building small basements, i.e., underground HAR plus space for a storage shelf and winter tires) have confirmed this to me: such orders would only come from Munich and Stuttgart residents with mini plots due to the price per square meter, and are otherwise not economical.

Even for a partial basement, one can, for example, assume 75% cost for 50% area or 90% cost for 75% area. So, a basement is usually more of a yes or no question, not a maybe.

A mix of many examples from various magazines...

Too many cooks spoil the broth. Homebuilders overload themselves with ideas, resulting in cramped designs, e.g., labyrinth-shaped.

Number of persons, age: 4 persons, 2 adults, 2 children, 3rd child not excluded

From the last sentence, I conclude that you still have some time until retirement. That means you belong to a generation in which rebuilding is not yet the rule but will be significantly more frequent than today. I doubt that a small apartment with a large roof terrace as a rental flat is really market-appropriate. So, away from the planning hypothesis of the care bed on the ground floor.

You will hear your washing machine and dryer in the living room; I wouldn’t do that. The new washing machines also have a very long running time (for us 3 hours) so that you will practically always hear something (especially since you are considering three children). The living room corner would definitely be too small for me.

Best regards
Sabine