Plot on a slope, height difference approx. 4 meters

No, that doesn’t say much. It could be that there is only 0.5 m difference in height within the building depth and the remaining 3.5.

Thanks for your answer.
In my profile picture you can see half of the property, but that probably doesn’t say much either?
After buying, we just have to get started and talk to construction companies. We would also like a split-level. We are quite open in that regard.

I’m attaching a picture that I took in February, which shows almost the entire property. It starts where my bike is lying.

We just need to get started and talk to construction companies after the purchase.

Why after the purchase? - You should know the height points or at least the contour lines of the property before you buy it. The planning can also show that it is not suitable for building.

In the pictures, you cannot see enough to assess the absolute slope. But you can see that it is probably quite even. So let's go with your numbers: 4 m over 33.8 m. That is an 11.8% slope, or calculated over 14 m of house depth about 1.65 m height difference. That would mean that split level fits quite well, or with relatively little foundation, the basement on the valley side could almost completely be exposed.

What are the requirements of the development plan (if there is one)? - Eaves and ridge heights would be important there.

It is very difficult to estimate the actual slope from photos. A site plan with elevation details could help. But I like the idea of the basement as living space.

Unfortunately, we do not have more precise information, and I do not know if I can get it from anywhere. The site plan, of which I have posted a section here, was provided to me by the mayor. We measured the approximate slope using Google Earth. Of course, this is only an approximate indication. Yes, I also think that a basement, which is converted into living space, can be a good solution. I also think a split-level.

Why after the purchase? - One should know the elevation points or at least the contour lines of the plot before buying it. The planning might also show that it is not suitable for good construction.

In the pictures, you can’t see enough to estimate the absolute slope. But you can see that it is probably quite even. So let’s go with your numbers: 4 m over 33.8 m. That is an 11.8% slope, or calculated over 14 m house depth about 1.65 m height difference. That would mean a split-level fits quite well, or with relatively little plinth the cellar could almost completely appear on the valley side.

What are the requirements of the development plan (if there is one)? - Eaves and ridge heights would be important there.

Hey, there is no development plan, that’s good. It was repealed, it is not a new development area.
Yes, the plot is very even, we also like that.

Hey, there is no development plan, that is good. It was repealed, this is not a new development area.

Repealed, why? A development plan also provides legal certainty, the "integration requirement" is a prime example of "lack of definiteness." So that does not always make things easier. However, in hillside locations it can be more advantageous than failed eaves height determinations.

We measured the approximate slope using Google Earth.

In the state geoportal you could find such information about your property. From the images it is difficult to estimate "reliably," but the slope overall seems to me rather low.