Floor plan design single-family house

Actually a nice design. However, I can't imagine that your basic requirement is to have 3 showers. Usually, the requirement is to have one! free! Then you probably don't have the requirement for a hallway to be 2 meters wide – free space and open areas are nice, but if you also want to have a garden and stay under 500000 €, here you have the option to reduce the house by half a meter. Even 1.20 would be enough... The storage space on the ground floor can also be divided into thirds: if you shorten the kitchen on the left side, place the [Windfang] there, you can completely do without the intermediate area (entrance, storage). The art is to deal with the square meters proportionally in order to stay within the cost plan. Anyone can draw big and bigger.

the two differently sized children's rooms could also lead to discussions (at least that was always the case for us as children)

What I notice:
- Guest room in the basement without a bathroom
- Double sink on the ground floor?
- Where is the walk-in closet?

And once again, it would make sense not to just post a floor plan like that, , but also to say a few words about what you like about it and where your concerns are.

And once again, it would make sense not to just post a floor plan like that, , but also to say a few words about what you like about it and where the concerns are

The concerns are not being able to accommodate all the requirements in the house without the house becoming too long.
Furthermore, the upper limit of 400,000 is an issue.

For the latter, some square meters will probably have to be sacrificed, if not also the double garage or basement, in order to implement what is seen here.
Therefore, the OP Konrad has to ask himself whether what has been drawn here are requirements or nice-to-haves: a large palace for a "small" budget usually does not work.

The concerns are about not being able to accommodate all the requirements in the house without the house becoming too long. Also, the upper limit of 400,000 is an issue.

Yes, that pretty much sums it up. As I said, the house was originally planned to be convertible into two apartments later. But we have probably given that up. Now we are wondering how to make the house smaller or come up with an alternative floor plan.

Regarding the points of criticism: No, we don’t need 3 bathrooms. The one on the ground floor can be a regular toilet. Or either on the ground floor or basement a bathroom with toilet, and a bathroom upstairs as well; that is enough. Regarding a toilet in the basement: we are not sure if that makes sense because a lifting system would then be necessary... This way, the two children's rooms will also be roughly the same size. The walk-in closet is included in the bedroom?!