What do you think of the floor plan? Do you have any suggestions?

YPG, why shouldn't the kitchen be where it is? We solved it similarly at our place. A 4-gable house and in one gable we have the kitchen, and the living-dining area is also on the side across the entire width of the house. Only the stairs and the other rooms we solved differently.

Exilhamburger:
I don’t like this hallway upstairs. Long, narrow, and dark. Unfortunately, many still think that a hallway is wasted space. But that is not the case. In our hallway upstairs we have space for a wardrobe, shoe cabinet, and mirror. I would leave out the small hobby room and just have a large hallway here or separate it from the hallway only by a half-height partition wall. That would make it feel much more open.
The dressing room will be quite dark, you will need artificial light here even during the day to see something.
For child 1 you don’t have a good spot for the wardrobe. Either you run straight into the wardrobe when you open the door or you block the window. As nice as big windows are, windows and doors should always be planned with a distance of 65cm from the wall to leave space for furniture.
Do you have a basement? If not, then the utility room will be quite small. If the technology and washing machine are in there, there won’t be much space left for anything else.
And I also see the problem in your living room that you always have to walk around the table to get to the terrace. I find that very impractical, especially with children or when you have celebrations.
For your guest WC I would move the door to the other side of the wall. That would create a nice niche for a cabinet or a coat rack on the right side of the hallway wall, and in the guest bathroom you would also have the opportunity to put a cabinet or some hooks for towels and bathrobes behind the door.

The hallway on the upper floor is very cramped. No two people carrying things should have to pass each other there...

And yes, how do you get to the shower on the ground floor? Where do you put your things (clothes, towels, etc.)?

But as I said, the stairs are just not right. So you better start over.

There should only be a guest bathroom on the ground floor. I had considered making the guest room a bit smaller and expanding the bathroom a bit more.

How else is the staircase supposed to go upstairs?

What is the blue arch above the construction area?

What is the blue arc above the construction area?

Rainwater retention basin

I don't find the stairs to be that bad. Friends have the stairs exactly the same way and it's not a problem with dirt or anything.

You can't say that like this. To what extent is one dependent on a building window? Does that affect the exterior dimensions of the house? Does the development plan dictate the roof orientation? Just try with an alternative. For example, entrance on the north side or change the stair orientation. Play around with new room layouts. Does it have to be the guest room? That strongly limits you on the ground floor. We originally wanted an office on the ground floor as well, but that way we would have lost a lot of space in the main rooms and it wasn’t worth it for us. Without a basement, a large utility room (the only storage option, laundry room and technology need space!) and another room on the ground floor is difficult to implement.