The walls look fine to keep working with. EDIT I noticed one thing. The wall group is glued to the plane below. You might find that disconcerting. You can use the “unglue” contextual command with the wall group selected.
I don’t know why the roof stuck to the walls-unless there were edges or groups somehow extending down the walls. If you look at the video, I did not touch any roof parts and therefore only wall surfaces and edges were selected. Admittedly I had to “lose” top of wall faces, to be picked up later by that method. Of course the best method is to start using groups as you start to draw.
In your model you should reverse the wall faces so only front faces face out /are visible. The style you are using does not show high contrast of back faces to front faces and that makes it hard to tell when faces are the wrong way. Try a style where back faces showing is obvious. And I dare say it’s hard to discern many things in the model when all is bright and white. Where you want that look, save that style for final output scenes. I use a “working” scene to take me back to a simple style that is clearer, faster, and easy to model with.
You’ll also want to group each cabinet and tub etc. Assign them to an FF&E layer. It’s nice to be able to just see the walls by themselves, and the best way is to group other items and assign them to separate layers from the wall layer.