[Bruno1337]

Now I know flip normals but now I have problem with invisible walls
I created object in sketchup and put him in blender and export....

https://imgur.com/a/mF9AymD

[AWhite]

I did not see the problem, you describe it better.
It is better to make a room with the help of a lesson on the Internet, where you can learn about all the "subtleties" of modeling. And problems should arise.