General recommendations/opinions/concerns

Unfortunately as a new post due to edit timeout:

Take a look at Zaba12 or at HansHaus - there you will find variations in comparable floor plan dimensions, both also in Bavaria.

Budget does not fit.
This is not feasible even with own labor and certainly not in two years.
Try to omit cost drivers like the extension.

Storage space is missing, a house must be self-sufficient and functional. This is not a 100 sqm extension.

Where is north?

Kitchen to the terrace

Living room huge
Mini children's room
Parent's room disproportionately large and impractical

Visit model houses and get an impression of sizes.
With this area, one more room, one utility room, and reasonably sized children's rooms are possible.

The child in the northeast still gets morning sun. I would immediately wall up the window. Possibly, the attic could also be converted into a purely parent/wellness area and the children moved to the basement?

It doesn't look like wellness at all. Our bathroom is also huge. About 2 sqm smaller and with a steam sauna. In the middle, it could also have been 1 - 2 sqm less.

The child in the northeast still gets morning sun. I would bricked up that window right away. Maybe the attic could be converted into a pure parents/wellness area and the children moved to the basement?

I am increasingly confirmed—thanks to such "constructive" contributions—that posting floor plan drafts apparently only triggers one thing in some people: to waste their meaningless lives by pounding out unconstructive babble. Do you treat your fellow human beings like this in real life as well? If so, you will end up lonely....
Such drivel—you can be very proud of that and pat yourselves on the back—has at least ensured that you will see neither floor plans nor house elevations from us. The time spent developing such a project can be better used.
May the sight of a candle flame enlighten one or the other.

The room layout on the upper floor is not really great yet. The bedroom is too big (just for sleeping). I would put both children’s rooms to the south (north is upstairs, right?). Then plan the bedroom and bathroom afterwards. The ground floor looks big, but the open plan area is fundamentally quite interesting. And it can never be too big – cramped situations can be avoided. Have you also worked with variants? Starting once with the kitchen, another time with the living room?