Replacement window with an attached partition wall

Unfortunately relatively dense. The groin. Are those the crossbars?

Now I know what the Leisten are. YouTube already helps. But whether I can get them past the wall, I can hardly judge. Otherwise, it does not actually look complicated. They are really just clamped.

Downwards it looks like you need to create a little more space. Then the glass bead should come out. Please do not pry in with a screwdriver or similar. Use a thin spatula or buy suitable tool for 5€ (Klotzhebel).

If you first remove a side panel, then it might be possible to pull out the top and bottom ones. But I would doubt whether the pane will come out, it looks too tight. You can see that placing the wall against a pane was not a good idea. I would shorten the area of the pane near the wall and then fill the space with a strip of styrofoam after installing the new pane.