How high does the house rise - how high to pile up earth (cellar depth low)?

Why does filled earth, which has been properly leveled and/or given enough time to settle, not hold permanently?

You must not underestimate that! Leveling alone does nothing; the slope must be properly secured against slipping, keyword erosion. It has to be terraced and retained. Since you obviously are not a professional, you absolutely need a specialist, namely a landscape gardener. You can't just have earth dumped somewhere and then simply pave it over. In my opinion, there is no quick solution just because the earth is coming soon. It first requires quite a bit of brainpower and a plan so that everything holds afterward (and looks good).

The terrace connects to the double-wing patio door and according to the original plan, it goes around the corner and ends behind the single-wing patio door. The latter might be subject to change if I take a path as presented in previous posts.

But isn't there only about a one-meter strip with a railing drawn in #20, or am I misunderstanding that?

For brainstorming, you would be going through way too many ideas at a 10-second pace.
You would first have to let ideas settle and sketch them out, then let them work for several days – with you, there are rejections in batches of ten.

No, I merely stated that I find it hard to imagine the raised terrace with integrated carport compared to the other things that have come up.

I looked at all the pictures again. Why was the plot graded flat across the entire width, even though it is supposed to be filled back in there?

Do you also have a section in the other direction with the desired terrain profile?

Overall, I can only emphasize again, if you didn’t have a professional involved in the planning from the beginning, you urgently need to get one on board now!!! This must be seen and assessed on site. Pictures often don’t show the whole reality. Perhaps simpler solutions will be found or there are more difficulties than the pictures show. I still see the drainage issue as one of the most interesting topics.

The shaft must remain clear.

The light shaft, which is needed on the left below the double-wing terrace door,

How does one now come to light shaft? So far, there is the sewage shaft, nothing more.

No, I merely stated that I find it hard to imagine the elevated terrace with integrated carport in comparison to the other things that have come up.

You have rejected almost all proposals across more than 10 pages almost immediately. When one acts so spontaneously without thinking and internalizing, this building design explains itself.

Tip: learn from mistakes and engage with the proposals and advice as well as tips!

Isn't there only a meter-long strip with a railing drawn in #20, or am I misunderstanding that?

The railing visible in the drawings closes off the terrace on the side with the single-wing terrace door. Below this railing, a retaining wall leads to the soil. You can see the retaining wall in picture 2; it is prepared there.