SketchUp gets shut down every time a make a line from one point to another above the wall

AutoSave_Untitled.skp (8.1 MB)

Do you mean when you draw in the edge shown selected here?

I’m not having any trouble with that. I’ve been able to draw in edges to start closing the tops of the walls without any problem.

There is a fair amount of bad geometry. Nearly all of the faces are reversed–should be white front faces out, not blue back faces. I would also suggest waiting on the textures until after you have the geometry modeled correctly. Textures can mask geometry problems but they will never fix them. It would also be a good idea to learn to use groups.