First of all, wow, great sketch. Top.
You wrote there is a bathroom in the attic, where is that?
Is the knee wall already built?
I tried to sketch it out with your information.
It's not as easy to plan as you imagine.
The first step from the planner is a cm-accurate survey. Since we can't do that, you have to provide it.
Lay the ground floor plan on the copier so that at least you can see something to scale. When copying, don't cut off the dimension chains.
Then take the copy and draw in the existing parts. For example, knee wall to knee wall, which will then be dimensioned exactly to the cm. The height of the knee wall is also very important.
I have noted the external dimensions, wall thickness, chimney, wooden supports, stairs, and windows. This shows that if the wall is on the axis, there are only about 3 m each to the knee wall on the right and left.
This results in a passage between the wall and the chimney of 1 m, between the chimney and the 2 m line 0.5 m.
Windows are very small, so it is difficult to bring light into the rooms. They should be 1/8 of the floor area. Bedrooms 3*4m are already only 1/12.
At least double-winged windows and/or floor-to-ceiling windows belong here.
Exact measurements are needed for the dimensions, otherwise it is difficult to help here.
Your way should be to go to a planner who can at least draw the existing state for you.
Then you can think about how to implement your ideas.
How did you renovate the ground floor? Everything without a plan?
Hehe, yes, I think that's the fundamental problem (and I'm sure quite a few users are at least screaming internally now), but that's how it was.
We went through the rooms, thought about what we wanted (and could) change. Then we had an on-site appointment with a structural engineer (who also said that the plans are only moderately suitable for assessment), talked everything through with him, he found our plans unproblematic, and we implemented them. I know that's not at all forum-compliant, but it works for us.
Accordingly, also the windows. We don't want to change them. They can't be made wider because there is already little space between the top window corner and the slope, and I find floor-to-ceiling windows awful. Maybe one could still think about roof windows. Although I have to say that the windows currently present in the rooms on the gable sides are also completely sufficient (if you're not thinking of a new build?).
Regarding the plan, there is a centimeter-accurate plan of the current rooms upstairs :). Only the external measurements might be a bit inaccurate because you can't measure behind the knee wall to the outer wall.
Copying the ground floor plan is a) difficult because it is not A4 and b) as I said, the original is already barely legible due to dilapidation, it won't get better with our home copier.
In the printed ground floor plan, you can also see, yes there is a knee wall/vestibule. I don't know if there are different ideas about that; it's just that a part of the room is boxed in (with wood and paneling), as you can see from the room dimensions, currently different in each room.
The bathroom is, if you place the plan with the name to the right in front of you, the third room. So first the large one with windows on the gable side, then the stairs (2.8x1 I think), and then the room that is only two meters deep (because of the large knee wall) – that is the bathroom.