Extension of dormer roof single-family house 1960, solid

(first of all thanks to 11ant)
We can purchase a single-family house from 1960 cheaply, living area 106 sqm. It has a purlin roof with a knee wall in the 1st floor. Solid construction.
"Problems":
- Bathroom on 1st floor too small, only has a bathtub, no shower. (would be important to us, would fit in if the knee wall is removed/extension added)
- 1st floor "only" 2 (large!) bedrooms, which could become 3 small ones by room partition (with extension: slight increase in living space)
- Poor/no insulation of the roof in the area of the knee wall (--> living rooms 1st floor: very warm in summer, heat loss in winter)
--> ergo: roof should be removed and newly insulated and re-roofed anyway, possibly combined with "living space increase" through extension

Has anyone done this? Remove roof covering, dismantle roof truss, (remove knee wall), build up 1m outside wall, new roof with appropriate insulation? Is this sensible for a 60-year-old house if the condition is otherwise solid? Which structural problems could arise due to the knee wall/the new outer wall? What problems can occur during implementation? In what range can the costs be? (yes, it varies nationwide, I know. But more like 80k or rather 150k?)

Attached is a side view (drawings not to scale, but approximate, to illustrate my question again; red = current "knee wall", green = extension masonry and new roof). Many thanks and have a nice Saturday.

I hoped you would be smart enough to upload more drawings from the construction file here right away. As I wrote earlier, I fear the delays are indicative that the operation is more complicated than you imagine.

I only have one floor plan of the 1st floor.

This way you quickly jump into the two-story structure. Is that still allowed according to the development plan? Otherwise, many things are possible. I would talk to an architect who is familiar with renovations.

That quickly leads you into two-story construction.

I don’t really see that here. My concerns are more about economically "appropriate" feasibility.

What does the roof frame look like? What does the roof covering look like? Is the ceiling above the ground floor made of concrete? In my opinion, the exterior walls should be able to support it well if they are made of masonry. What have you planned for the additional floor? What does the building authority say about it?