That will not work like that, sorry. You always have to plan everything together on the slope. Every surface – even if it is just a carport – must have a foundation. For this, you have to comply with the distances to the street. This can lead to the fact that you have to cellar the parking spaces on the slope. That also makes a mega paved courtyard on the slope somewhat absurd.
The development plan is available in your municipality. It is accessible to the public. Many are also online. If there isn't one, you build according to Paragraph 34. Here, too, you can inquire about the conditions from the office. You can also leave everything to the architect, but "not knowing" usually costs extra.
The architect drew floor cabinets under the slope for you? Very doubtful. I would even ask to see the diploma.