Simple single-family house hopes for optimization tips

A few measurements would be helpful in the plan.

What is the "WA" supposed to mean? Supply shaft? If so, that becomes interesting regarding the piping for wastewater in the upper floor bathroom. All around...

What do you want with this small staircase, as well as the small doors? Are you that small?

I would place the guest room directly in the basement.

If I may quickly:

Please don't consider only "what would be ideally cut for us" in your planning!

Important factors are especially:
- Is the whole thing even statically feasible and if so, how would the desired layout affect the construction costs (e.g. how are the ceilings constructed and where do they rest (load-bearing walls ...), are beams necessary (when I look at the large open kitchen into the living room ...))
- Where do all the supply lines run, for example? There's practically no wall directly above the other ...
- Staircase with 2m width ... won't work ... there are corresponding minimum dimensions that must be met (rather calculate with 2.4m)
- How does the house look from the outside? The windows also all sit "somewhere," which (in my opinion) doesn't look so nice in the end.

Basically, everything is possible at first ... but that is also a question of money! And 450K EUR for the house with basement will be, in my opinion, very ambitious...

Best regards

- Staircase with 2m width ... will not work ... there are corresponding minimum dimensions that must be observed (rather calculate with 2.4m)

A staircase with 2m works. It's not spacious, but it works. However, the staircase in the picture is smaller than 1.80m.

How high is the probability of a third child?

At 29, menopause is still not in sight, even in clear weather ;-)

What is supposed to mean "WA"? Supply shaft?

Laundry chute

However, the staircase in the picture is smaller than 1.80m.

Yep, 175cm...

Laundry chute

In this case, the sanitary area probably won't work like this anyway. I don't see any dedicated pre-wall installations or similar...

In addition, after longer consideration, I find the views of the building very odd for me (especially when I look at the windows and their positions). For example, on the upper floor facing the garden, only one window (in Child 2).