Floor plan single-family house approx. 160m², main entrance in the basement, north slope 1700m²

To the kitchen

I would definitely go to a large specialized forum for that.

It is still too early for that ... first the clarifications need to be made that and have mentioned.

In my opinion, you can raise the basement a bit. That saves you 2 levels. The mezzanine can also be a bit lower.
You can then accommodate the excavation under the CP and the driveway. Where exactly is the water pipe? Is there an entry for it in the land register?

I have two plans where the water pipe is marked. I hope that helps and thanks for the reminder.
The pipe runs on the street plot.
Don’t be surprised, we also purchased the property with an approximately 30 sqm triangle at the driveway to be able to realize a private entrance without an easement. This is not shown in the older plans here.