Single-family house on a slope with a basement for 2 people including home office and hobby rooms

And describe exactly what you want. So be honest: Playroom for different possibilities is simply not a dominastudio - the requirements are somewhat different there, I think.

There should be a kind of library in 19-something style, for art and literature, but since I have no idea about that, it can also be 18th century. My wife's wish for a long time. So I have to disappoint you, no dominastudio

I would save myself the trouble in your place. Put this in the hands of a decent architect, I can only warmly recommend that to you. And also deal with the financing early on. The statements "because I want to have it paid off quickly" and "we could certainly afford more" don’t sound like you have already done that.

Oh, a garage with 6m is not oversized either. Ours is 7.15m. I still want some storage space for bicycles, tires, etc.

Tires and bicycles should go in the basement. In fact, we only had a financing consultation and nothing else. But since I myself come from the financial sector, I am not unfamiliar with the whole thing and I didn’t learn anything new during the financing consultation. They only asked how much the house should roughly cost, then I said 500,000 and he presented and explained some repayment plan overviews with the key data. He always wanted us to pay it off forever because the interest rates are currently cheap, but I don’t want that (and it doesn’t make sense to me either). We can definitely manage a monthly rate of 2000. 3000 would also be possible according to the household budget, but I would like to have some buffer. Currently we pay 2000 rent and on average save about 1200 per month. Saving up equity.

So my floor plan has been approved by 2 architects after a few minor changes that I made beforehand. It still worked out today because they were actually very interested in the house and another architect whom I don't know was invited. I had it drawn freely beforehand. However, they then found mine great.

I would still be interested in your specific concerns. So that I can still incorporate them. But for that, I need a bit more concrete input. So, that I have made a sequence of rooms. The architects' statement was "yes, that's exactly the point and that is a very good sequence of rooms."

So, my floor plan has been approved by 2 architects after a few minor changes I made beforehand.

Strange, usually the client approves the architect's floor plan. To me, it still looks quite amateurish. However, I am now having trouble understanding the 3 floors and the property. Here is the ground floor, there is the basement, which still needs to be changed, and in between are the new drafts. And now this mess has been approved by some architects? What do they have to do with the project? Are they hired? Two of them? If I am paying 2 architects, then I would expect a professional draft including a cost estimate. Spending well over 500K while you as an architect are also trying it yourself on a slope, I find that quite thoughtless.

Funny, normally the client approves the architect’s floor plan.
To me, it still looks quite amateurish. However, I am now also having trouble understanding the 3 floors and the property. Here is the ground floor, there the basement, but that still needs to be changed, and in between the new drafts. And now this mess from some architects has been approved? What do they have to do with the project? Are they engaged? Two at once? If I pay two architects, then I would expect a professional draft including a cost estimate. Spending well over 500K while you, as an architect, are still trying it out yourself on a slope, I find that quite reckless.

My wife has been friends with the architect since childhood. We have already had an appointment with him regarding the construction. Now we have another appointment in May. However, today we were invited due to a birthday and are still there. And his colleague was there too, and then they somehow discussed floor plans thoroughly and at the very end I presented my floor plan after they had already drawn floor plans upon floor plans. Because they simply enjoyed dealing with it.
And they found it great to realize. They would make it more open, but if you want it that way, it would be great. Definitely feasible and sensible.

Now we have another appointment in May.

I would never hire a friend as an architect. In case of conflicts, the friendship ends very quickly because the amounts involved are often existential. But then we like to wait and see what comes out in May.