Is it advisable to buy land with a slope of 3 meters? - Experiences?

Here is the plan excerpt. So looking at the plan, south is on the left. Then it probably won’t work with the property?! So the terrace would then be facing west and thus into the "slope"

The slope is borderline for a slab foundation. A 3m wide terrace would be approximately 1.30m below ground level. It is doable, possibly in two steps. If you have the terrain modeling done by a landscape planner, the savings for the basement will quickly be relativized. If you yourself have skill and enjoyment in garden design, the slope offers very nice possibilities. If you just want a meadow for playing soccer or badminton, look for another property.

You just want a meadow to play football or badminton on, look for another property.

Yes, good luck with that. If there are so many properties available where you are, then I would keep looking.

That was also our thought, to excavate the area for the floor slabs plus the terrace and then create a slope up to the original height. But we definitely did not want to build a basement or a recessed floor or something similar, but "only" a ground floor and an upper floor. A classic single-family house

The classic single-family house usually doesn’t work on a slope. But that’s why you can rearrange things a bit:
For example, already said it the way I would say it: basement and ground floor, without a cellar. Only that a bit, well a bit more is embedded in the slope, that would practically be a half-basement. You could use that for utility rooms.
You can also place the terrace on the south side, right?
So, you could rotate the house, make the driveway on the north side, and so on.
Would that be an option?