Single-family house 150 sqm basement with 15 sqm upper floor in the outdoor area

I assume that what is described and depicted as [OG] is actually the [EG] and have dismissed that as a typographical error.

In my opinion, the OP does not need to provide reasons why they are building a new house only 2.5 km away from the existing one, why they do not want to accommodate guests, etc. Also, comments that the "old" house is so nice do not help. That is absolutely none of our business.

What is important are only the requirements for the new home. Based on the wishes presented, advice can be given. But clearly, some information is still missing, especially regarding the [OG] and, of course, more precise measurements.

Why? 9000 sqm would be a reason for me. Why it is planned this way is not clear. Large attic without use

I quite like the ground floor. But I don't understand the upper floor. Are you only planning 15 sqm here? What about the rest? It will hardly become a gallery if you criticize it as acoustically worthless in the current house.

No one should please expose their private life too much; nevertheless, it is difficult for outsiders to give appropriate advice on planning without knowing some circumstances from the personal/private sphere.
A good plan is built exactly on these personal habits and needs.
Since here, among other things, external/internal images of the current living situation and other usually private text are present, the child of data protection and privacy would already be in the well anyway. As a regular internet user, one should not worry too much about this anymore, since all our truly relevant data have long been processed.

Regarding the intended age-appropriate or even "disabled-friendly" building (even already in the old house? with stairs/gallery?), I notice the following contradictory descriptions:

Plot approx. 9000m²

That hardly seems like an age-appropriate/disabled-friendly decision, not least because of the following…

Do you have employees?
No.

Who does it then?

The attic extension exists because we like it

Absolutely beautiful but hardly age-appropriate

So "disabled" friendly.

...and certainly not that either

Imagine if you walk along the possibly open staircase into the living room and look directly outside through the 4x 2.80m large window

... ergo, the old house is nice but neither age- nor disabled-friendly

I don’t see it that way. Since I always manage with a ladder.

In general, I believe that "disabled-friendly/age-appropriate" is often used as a striking argument in sales talks.
In reality, it is certainly not enough in the daily life of a physically or mentally frail/disabled person to merely make the doors a bit wider or to build a few fewer thresholds, as is often done.
I think that TE wants to build a nice house for themselves, which I can only too well understand, but I do not fully understand the stated self-evident aspect of age-appropriate/disabled-friendly building in the true sense here.

The reasons are quite simple. We are just moving 2.5 km further. I have attached a few photos (the first three). I believe I don’t need to say much more then

When I look at the photos of the old house, I can see other houses and many (sorry, ugly) welded mesh fences through the windows. The new house, on the other hand, is supposed to be built on a huge plot in a secluded location with a view of endless meadows and forests. So I would also move 2.5 km right away.

I probably wouldn’t place the bedroom facing south if everything around is green. Or windows to the east? It won’t get as hot in summer then. The dining table docked to the kitchen island makes the open-plan kitchen seem a bit narrow and I think it might be a bit inconvenient if you always have to walk around the 4 or 5 meter long kitchen-dining table island, even when setting the table. Maybe plan something nice with a corner bench?

Upstairs you can leave the rooms unused except for one office. In case the attitude towards guests changes or if the house needs to be sold, you will at least have a backup there.

If money is a minor issue, I would make the entrance area a bit more representative. It feels quite narrow and cramped. Without dimensions, though, that can be misleading.

Overall, it will surely be awesome. You already proved that you can do it with House 1. Hopefully, the new house won’t need as many gabions and welded mesh fences.

Yes, I would reconsider the hallway overall. When entering the house, you immediately run into a closet, and the hallway then winds around the corner to the bedroom. In the most recently attached pictures, you can see that this is also the case in the current house. That would be too narrow for me. And in the new house, towards the bedroom, it is also too dark.