Fixing an overlap problem in Graphics[ ]?

Hi everyone!!

So for a project in uni I have to code a floor plan in Mathematica. It’s been going great, but now I have a big problem I’ve been trying to solve for the last two days, but failed miserably. As you can see in the screenshot below there is a wall in room three, that is not there anymore when the walls are extruded, Plus there is this dent in the other wall… And I don’t know how to fix it.

I really need your help, thank you so much!
(I’ve gone ahead and attached the whole file as well as the screenshot below.)

Florian-Weinke.nb (4.45 MB)