Floor plan of a single-family house approx. 160m², hipped roof, with basement, hillside location

I still do not see the draft as so catastrophic.

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Something like that.
You have to cut back anyway, that is also factored in with the horrendous incidental construction costs...
The program can’t show everything: I used your plot as a template. The house is set forward and narrower, but also wider up to 3 meters to the boundary. I haven’t really planned the basement yet, but briefly indicated where utility rooms and living space could be. The garage is partly basemented as living space up to the 3 meters. Overall, you save the entire utility basement, but it still comes to about 160 sqm... okay, some brainpower is needed, since I only quickly put in the 10 cm walls.

We also bought a hillside house with 3 floors last year. I think the architect implemented it quite well. The basement was built entirely as a living basement. In terms of external dimensions, it is slightly smaller than your plan at 9.60x7.60m. On the upper floor, we have the bedrooms and the bathroom, on the ground floor a living area with open kitchen, utility room, and guest WC, and in the basement a small bathroom, a small and a large cellar room, and 1 large room that could of course also be made into 2 rooms.
The outdoor areas were designed on 2 levels with retaining walls made of natural stone on both sides of the house. On the level of the ground floor, we have a carport on one side at the front door and a terrace on the other side. On the basement level, we have another terrace, a garden house, and the rest is lawn area or garden.
On both sides of the house, you can go down to the garden via stairs also made of natural stone.
What the whole thing would cost today, especially until you have finished the outdoor areas with retaining walls, etc., is of course the big question. You just have to be able to afford it. But building on a slope is always more expensive.

Can you name me a freeware with which I can represent this similarly and visualize my thoughts? aptly described my property as "prescription-only" and honestly, I can't find anyone with their own ideas except the people here.