Building on a slope with approximately 30 percent incline

ufff will be expensive

Wooden frames have a static problem on slopes and tend to become tower-like. Basement/apartment pushed underneath. Would not be my choice on a slope.

Do you have a few more details about this? I would be very interested.

Rear wall, floor slab, and ceiling must withstand the pressure of the slope. The classic timber frame is too light for that. The tightness of waterproof concrete is also not sufficient.
Companies make money on their walls.

Proposed solution 1)
Cellar used as a utility cellar/secondary apartment underneath
Proposed solution 2)
Retaining wall and a house on a floor slab about 100 to 150 cm in front at a distance
Proposed solution 3)
Basement with masonry/concrete living spaces, the rest of the house as a timber frame, correspondingly smaller.

No one offered us option 3 voluntarily; on the contrary, there were refusals. There are also some who do that.

Option 2) usually means more earthworks. In any case, it creates a shady spot. It negates the advantage of garden access from 2 floors. The property must allow for the wasted space.

Option 1) Secondary apartment/utility cellar results in unnecessary square meters, higher costs, one more floor.
Garden access or balcony from the living level.

Timber frame is not bad. Simply difficult on a slope and therefore not the first choice.

Rear wall, floor slab, ceiling must withstand the pressure of the slope. The classic wooden frame is too light for that. The tightness of waterproof concrete is also not suitable.
Companies make money on their walls.

Proposed solution 1)
Basement used as utility cellar/secondary apartment
Proposed solution 2)
Retaining wall and a house on a floor slab about 100 to 150 cm in front at a distance
Proposed solution 3)
Basement with living rooms built of masonry/concrete, rest of the house as a wooden frame correspondingly smaller.

3) no one offered us that on their own, on the contrary, there were refusals. There are some who do it though.

2) usually means more earthworks. In any case, that creates a shady spot. This negates the advantage of garden access from 2 floors. The property must allow for this use of space.

1) Secondary apartment/utility cellar unnecessary square meters, higher costs, one more floor
Garden access or balcony from the living level.

Wooden frame is not bad. Simply difficult on a slope and therefore not first choice.

Thank you very much. Assuming that direct (i.e. without stairs) access to the garden is not necessary, would such an approach basically work (if a plateau is already present)?

if you don't have to catch a slope it should work. you still have to plan the outdoor area. many use the house wall as a retaining wall so that the garden behind it is level

if you don’t have to catch a slope it should be possible. you still have to plan for the outdoor area. many use the house wall as a retaining wall so that the garden behind it is level

yes, but for the reasons you mentioned, that wouldn’t work with a timber frame (without concrete foundation). you basically have to decide how much slope you want to remove from the property (e.g. for a level garden). if you can really live "on the slope," that will probably keep costs somewhat more reasonable.