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

Piling up creates a hilly landscape that a) looks modest and b) worse, will not last permanently.

Why will piled-up earth that has been properly leveled and/or given enough time to settle not last permanently?

I don't imagine that to be nice.

Well, you can practically use a raised terrace here as a carport or vice versa. In the end, I don't care how you waste your money. With a carport/terrace, you kill two birds with one stone.

Terrace door level only in the area of the terrace,

Where _is_ the terrace? I still don’t see one, only doors leading to nowhere. And that’s why I’m also asking where the doors lead, where the kitchen is.

I prefer the solution of filling up to the terrace door level only in the area of the terrace, paving a normal terrace there

Then do that. Start filling up and then you’ll see the problem or not. The shaft must remain free.

Why won't piled-up earth, which has been properly leveled and/or given enough time to settle, hold permanently?

Keyword erosion. The steeper, the more likely. You have to secure it properly, e.g. with walls or suitable planting or the like. You don't have much space for terracing.

but the brainstorming is just getting started.

But for brainstorming, you go through way too many ideas at a 10-second pace. You'd have to let ideas sink in first and trace them, then let them work for several days – with you, there are rejections in packs of ten.

I would rebuild all of this with Lego. Then you can immediately see where it gets steep, where a wall is needed, or where it just doesn’t work, the first thought ;)

Where _is_ the terrace? I still don’t see any, only doors that lead into nothing. And that’s why I’m also asking where the doors lead, where the kitchen is.

The terrace adjoins the double-wing terrace door and according to the original plan it goes around the corner and closes behind the single-wing terrace door. The latter might be under consideration if I take a path as presented in previous posts.

Both terrace doors (double-wing and single-wing) lead into the living room. The kitchen is where the heat pump can be seen outside.

Then do that. Start filling up and then you will see the issue, won’t you? The shaft must remain free.

The light shaft needed to the left below the double-wing terrace door should be closed at terrace height with a translucent steel grate. That area should then not be paved.