Driveway planning for large sloped property - 25% gradient

the current building window, closer to the street, is practically directly on a steeper slope

The contour lines say otherwise. According to them, the house should be placed as far south as possible, since the height difference there would only be 2m instead of the currently planned 3.5m.

however, this would then be very, very deep in the ground (4-5 meters below ground)

Yep.

So everything would have to be brought to the house via stairs.

Yep. Or by freight elevator. But that's just how it is in the mountains.

The view from there is truly breathtaking ... The house itself will have a garden level (touching the slope on the northeast) and a ground floor and will fit perfectly there.

I have left the house as planned, only shifted 3m toward the street so that it lies about 1m lower. Whether that significantly reduces the view, I don't know.

Placing the house further down would not make much sense either, as we would then have more garden uphill toward the forest and northeast, which would be difficult to use.

In the southwest it would also be difficult to use, since the driveway is currently planned there. But as I said, way too much information is missing. A completed questionnaire from the pinned first post would be very helpful.

Thank you for the answers!

The plan can unfortunately be a bit misleading, as the green area was not measured in such detail.
The fairly straight line that separates the green area from the white plateau is currently a fence.
Behind it (towards the street) it drops quite steeply by about 1 meter, followed by another plateau that then slopes quite steeply down to the street.
An area by the street is already secured with a wall (heavy-duty wall). This would possibly need to be moved slightly for the driveway.

As requested, here again is a summary of the key points:

Plot size: approx. 2000 sqm
Slope: Yes, from southwest to northeast, about 20m incline over 50m – not a uniform slope
Floor area ratio: 0.4
Floor space index: 1.2
Building envelope, building line and boundary: see plan (first page)
Adjacent development: NW built-up (lower, as the slope runs slightly differently there), NE forest, SE still undeveloped plot, SW street and houses behind it, the house height there should not exceed 10 meters – as it is the mountain side
Number of parking spaces: should be enough for two cars
Number of floors: 2 (basement level in slope, ground floor above, an attic with living space is also allowed)
Roof type: flat roof
Style: modern – driveway, garden, etc. can also be somewhat rustic
Orientation: south (SW)
Maximum heights/limits: max. 13m from base plate to roof edge
Further requirements: garages/carports must be within the building envelope

Our requirements would be that the view remains. For that, the house should not be set too low, and we do not want to build too close to the street.
A terrace will presumably be located on the SW and SE side of the house, with the garden then to the SE. Between the house and the street there will be greenery (bushes, possibly a few smaller trees).
This greenery is already present and – as far as possible through earthworks – will remain according to the landscaping gardener (also to secure the slope a bit further).

I don’t know anyone with such a long driveway; we have enough slopes here. Flat plots are rare.
We have 15%, which is more than okay.
My parents have almost 30% and my in-laws a bit over 30%. Short and steep. In winter you best sit down and slide down, high heels are hell.
Maybe consider separating the garage from the access path. The car stays down, you take the stairs, and for transports there is a driveway, whether for a sack truck, wheelbarrow, or car is up to you.
didn’t you even consider a freight elevator?

Are the 30% slopes at your parents' and in-laws’ houses still drivable by car in winter? What type of surface was chosen there?

What we can also well imagine would be to create a stairway and a walkway in addition to the driveway (maybe partially as slope support). Then only cars would have to manage the driveway.

So I lived for 20 years on a street with a 20% incline; and NO, it is not drivable in snow and ice early in the morning; some people install heating coils in the street. But winters are getting milder anyway.

Without spreading, the driveway is passable and walkable neither at my parents-in-law's nor at my parents'.

Thank you for the answers!

Without spreading, the driveway is neither drivable nor walkable at my parents-in-law's nor at my parents'.

As long as the driveway is walkable after clearing and spreading, that's already good. I was afraid that it would be impossible to clear and spread it myself at 25%. How is the surface? Gravel or paving?

But maybe someone else has an idea on how to avoid the 25%.

Does anyone have experience on how tight a curve should be to still be comfortably drivable with a normal car? I know that according to road construction regulations a radius of 12.5m is required, but since I probably don't want to drive the driveway with an articulated bus or semi-trailer truck, a smaller radius should be possible, right? That way you could add a few more meters to the length of the driveway.

Well, clearing and spreading is not fun. Ask my tailbone. You also have a long driveway. Replaces the gym. It’s not just quickly cleared. Curves just not too small. Behind our house cars often slide around the fairly steep curve or park in the wall or guardrail, and this is not a delicate street. How are the winters where you are? You only specified Bavaria. @Escroda‘s suggestion has something. The driveway costs real money. Will you be happy with it during the winter months?