Single-family house approx. 180 sqm in a rural location

In the end, you have to know it, but I think the area in the hallway is clearly too large. The wish could also be implemented with a spiral staircase or even easier and more space-saving than with a straight staircase. A straight staircase is simply designed for a straight hallway.

then you could also create equally sized children's rooms on the upper floor. What kind of roof will the garage have? What about the suggestion for a basement in the hillside location?

I hope the information is enough for now

Unfortunately not. Especially this information is crucial: Personal price limit for the house, including equipment: We dislike discussing castles in the air The resolution is too bad but that looks like roughly 13m x 10m external dimensions and there the exterior wall doesn’t even have the required 40cm thickness. Slope: see attached picture - Where is the road?, how big is the building window? Dimensions are crucial on a slope, do you want to backfill 2m? Are costs for that already planned? Leave the planning to the professional first. He has learned it and you have to pay him anyway. Planning yourself as an amateur on a slope is nonsense.

Personal price limit for the house, including equipment: We have one, but I do not want to comment on it for now and will wait for the offers from the construction companies.

We will discuss the proposal for a basement, but I was rather thinking of backfilling since we have about 180 sqm of space
Here is the property including the building window as an attachment.

You don’t have a full floor on the upper floor. This means your 180m² will not be fully usable and the filling at the hillside costs a lot of money. A truckload of [Mineralbeton] costs about €500 for example and you will need quite a few of those. On top of that, a lot of humus and soil.

The basement on the garden side can also contain living spaces. Modern basements have nothing in common with the damp, dark, oil-smelling cellars of old times.

I understand that the upper floor is not a full storey. Otherwise, there would be more square meters. I assume 2/3 for the upper floor.