I also find it pointless to plan such a spacious house with all sorts of frills (balconies, garages, basement, numerous bathrooms, etc.) and set the budget at 350,000 euros. For this amount, others build a very simple house without a basement. So before going into detailed planning, I would first clarify the financing. You can expect about 2,000 euros per square meter of living space without recesses, balconies, extra bathrooms, etc. In addition, there is the basement (for a house of this size certainly 80,000 euros), ancillary building costs, painting work, flooring, and complete furnishing.
Landscaping your embankment with stones will definitely not be cheap either.
Best regards
Sabine