Land planning for a house on a gentle slope

Once again summarized: The question is why you want to build a house that is not suitable for a slope. Sure, you can add a basement, which only seems attractive because you can incorporate the word [Einliegerwohnung] there. But for yourself, that is, for you, it remains a house without significant own-home character, meaning without access to your own garden. If you commit to a sloping plot, this applies to you as well as to the architect, then do it properly. She is not doing a good job if she wants to "sell" you this house.

Summarized again:
The question is why you want to build a house that is not suitable for a slope. Although you can have a basement, which only appears attractive because you can call it a granny flat there, it remains for yourself, that is for you, a house without significant homeowner character, meaning without access to your own garden.
If you commit to a sloping plot, which applies to you as well as to the architect, then do it properly. She is not doing a good job if she wants to "sell" you this house.

100% my opinion. How else do you get into the garden besides through the granny flat? Through the stairs?

The design looks very much as if the architect is overwhelmed with the plot and/or has never built a house there before.
Based on the design, the plot demands: front door on the street, sleeping upstairs, living and kitchen on the ground floor with a level terrace.

*does not scream writes