Fortunately that type of error message usually does mean it is fixable. Most of the time it just has to do with how the model is created.
If it’s not too much of an issue, you might want to start over with the walls and doors. It would be better to draw them separately and use components. I’d also not leave the tile drawn as you have it because those coplanar edges could easily be erased.
If I had to guess, I’d say you drew a rectangle on the ground plane, outlined the walls and then use Push/Pull to pull them up to height. When you do that, it’s normal to see the faces reversed. You can correct the face orientation after you extrude them or, if you deleted the faces for the floor, the face orientation would correct itself.