Renovation of children's room - split one window into two windows?

To stick briefly to the other idea, you can leave the one room with 2 windows and give the other room a floor-to-ceiling window. Since the niche in the lower room fits better for a wardrobe, you don't need to get any light INTO the niche there.

well, the problem is exactly where the new wall is supposed to go.

You can mediate or measure that yourself. I don’t understand the problem of "where" the wall should go. In that option, you have the cost of three walls.

that’s the solution marked as expensive in the first post by me. Theoretically, I like that one best, but practically I was also hoping for an idea of what that might cost?

In my option, you have the costs of two walls, but including removal and installation of the windows. Correct me if I’m wrong, but there should be windows that have this insulated central post, so that masonry and insulation work are omitted. Then it’s the cost of the third wall versus the new window.

If you build the partition wall yourself, you should be able to calculate these costs based on your required materials.

By problem I meant which variant it should be. The Z-shape where all three windows remain, or a straight wall where the middle window is divided into two windows.

The insulated central post I find interesting. I have to ask a window manufacturer about that.

If the rooms are to be the same size, a straight wall can be installed so that the room at the top of the plan has two windows and the room at the bottom of the plan has one. The middle door will be closed. Whether the room at the bottom of the plan is bright enough can perhaps be tested (how exactly, the location would need to be known). Are there roller shutters? Depending on that, the lower room could then receive a larger/new window. The minimal solution (for two equally sized rooms) requires removing the partition wall, installing a new partition wall, closing the door (i.e., frame out, brick up ...). The costs depend on that (DIY yes/no; other conditions and later renovation effort, floors ...). Or am I completely wrong? What is wrong with this solution?

thanks for the suggestion. I had also considered this solution, but unfortunately the rooms will not be the same size, but approximately 12.5 sqm to 18.5 sqm.

For me, the long edge is 7.81 m, half of that is 3.9 m. Now you measure 3.9 m from the bottom of the plan and draw the new cross wall there. The middle window starts 4.25 m measured from the bottom of the plan. What did I overlook?