Floor plan of single-family house approximately 145 sqm with west access

We are not sure whether the fixed window on the ground floor makes sense or is even used.

Due to lack of use, the couch is now placed in front of it.

Due to lack of use, the couch is now standing in front of it...

And it looks good.

In a square bay window seat, comfortable seating is only possible for a few adults but for most children. Anyone who has the image in mind of lingering there to gaze out absentmindedly or read a book will hardly be able to realize that. When a few more people are in the living room at Christmas, such a window seat can be a great place where children can sit and/or play. Even when guests are present and you want to sit not awkwardly at a corner but more communicatively in a circle, a window seat is a great feature that saves space. This way everyone fits in without needing more square meters. (However, in your design you have some unused square meters if you look at the area between the drawn-in sofas and the dining table.)

We don’t have a window seat, but a stove bench. It is not used very often, but now and then very much appreciated. That is worth it.

I have improved the entrance to the living room. 80 cm is far too small. I would plan it even larger.

The island a bit longer and a window in the line of sight.

I like this , even though virtually no one sits there. The "usual" window seats, known from Pinterest etc., mostly have a protruding wooden cladding throughout the entire reveal and that is 1. expensive and 2. space-consuming if it protrudes; but as shown in the picture it is stylish and it doesn’t bother that the sofa partly stands in front of it. That, in turn, would speak for a higher parapet than we have in our place; also for that reason, TE should urgently draw in measured, real furniture.
As it looks with you, you have a wall thickness of at least 40cm and the window is flush with the outside. In the previous thread on the topic and also here in the plan, however, the window is planned in the middle of the outer wall and then this monster juts into the room like a cupboard.
This picture shows you the key data, also regarding parapet and depth; the additional costs are only in the somewhat larger windowsill.
Your personal background on the construction is still missing, so it is not clear why you are planning an expensive basement, the use of which you (except for the utility room) apparently have not planned for yourselves at all, the rooms are probably just there. Are you really TV freaks (home cinema in the basement), then I would at least have a toilet downstairs, although I would have that in the basement anyway; but then I would completely eliminate the TV on the ground floor in the design. A high six-figure amount for 55 sqm of freely usable basement space, which I might or somehow need someday? That could be done cheaper and more comfortably without it.

Living space max. 145 sqm

... as a living space requirement? Why that, if then so much money goes into a basement and you are now still looking for an office room?

The bathroom on the upper floor could be bigger, but we are also satisfied with the current size.

Also here: "...bigger" - but why. What is supposed to happen with the extra size? A too large bathroom is usually uncomfortable if there is not a specific planning idea behind it. I think that already 12 sqm is too big, especially when you are already looking for an office room. Likewise, children's rooms do not need 18 sqm, but rather a clever layout for desks or niches and shelves; sheer size is meaningless.
Furnish your bathroom with real furniture and appliances and please also draw in stud walls. So far this is not really a plan, but simply everything placed. From this, the need for window position or also for the toilet etc. arises more clearly.

Why would you plan a chimney when you have a heat pump?

Furnish your bathroom with real furniture and appliances as well, please also draw in the partition walls. So far, this is not really a plan, but just everything placed. This then gives a better idea of the need for the window position or the toilet, etc.

The bathroom is not furnished that badly. You can barely see the shower. It can also be a bit smaller.