Problem with the ceiling and floor clearances

Hello you hardworking house builders,

I had already reached out here a while ago regarding floor coverings for a luxury house I am working on for a school project and received many helpful responses. Now, unlike the "normal" student, I did not submit my work a few days late but, being the good person I am, a full 3 months early... ;-P I wanted to use the time to thoroughly check my house and noticed a few defects that I wanted to fix before submitting. For example, when I determined the ceiling thickness, I completely forgot about screed and floor coverings and accordingly also planned the stairs. It would have been a great house, just unfortunately without floors... +^^+ A bit embarrassing. Starting with this "problem," which was quickly fixed thanks to an eraser and calculator, I found more and more construction issues. The best part is that basically the solution in one place becomes a problem in another.

I’ll give you some key data about the house:
Plot ratio (Grundflächenzahl): 0.2
Floor area ratio (Geschossflächenzahl): 0.4
Plot size: about 5,000m² to 8,000m²
Maximum number of full stories: 3
Living area without basement (which still needs to be planned): 1,169.24m²
3 full stories present, 2 at 495.52m², 1 at 178.2m² (all exterior wall dimensions)
Ceiling height ground floor: 3.00m
Ceiling height 1st floor: 2.70m
Ceiling height 2nd floor: 2.70m
Ceiling thickness with covering: 0.36m
Stairs: step height approx. 0.17m; step depth approx. 0.30m
Basement (tentative): 608m² >> 38m x 16m

That’s the basic data. If you need more info, just say. I’ll provide whatever I can.
Now to the actual problem, I hope I can explain it reasonably well. The house is built somewhat like a flattened T, called a "Vorbau," I believe. The house is to be basemented but not in the same shape, rather in a rectangular form, meaning the basement is larger than the house above. So far no problem until...
...the part of the basement that protrudes beyond the house is supposed to be planted with grass, etc. In order to cover as many plants and not just grass, I planned the depth to be 100cm, that is 1m. From my design the following problem arises: between the floor of the ground floor and the ceiling of the basement, there is a distance of about 150cm. From what I have read on the Internet so far, I gave the floor slab between basement and ground floor about 50cm PLUS screed and floor covering, so about 65cm to 70cm. Now there is still about 80cm to 85cm of empty space there, which must not be there. Do you have any idea how I can solve this?

Thanks already for your great help and I hope to hear from you soon.

Regards

C.

Approach it from the simple side: How much soil do you really need for plants and grass? Normally, 30cm is enough to plant lawn / roses etc. The problem is rather: Where should the water go when it rains. How do you drain the water along the upper side of the basement so that no swamp forms there. If you can plan freely: Mark a gravel / crushed stone area in your plan with different colored gravel and place potted plants on it, looks - if done nicely – very classy.

Would a glass roof for the basement be an alternative?

Rather less... The sections in question are relatively large. In addition, one part is located directly above the underground garage... Therefore, a glass roof is actually not an alternative.

The areas on both sides measure 7.40m x 7.60m. That is actually too large for me to pile gravel there...