I tried working with the blend file, but didn’t make much progress. I straightened out some of it, but tbh some of the topology needs to be redone. There’s a corner that has a lot of disorganized vertices, and it’s very hard to tell which are connected to what. I don’t know what the extra vertices are meant for (what detail you are trying to add with them).
I recommend deleting the entire right-hand side of the first set of stairs (the stairs that connect to the salon floor), and replacing it with something much simpler. I would have deleted it, but I can’t tell which vertices are part of it, and which are part of the next railing.
For this scene, I would start simple, get the dimensions right, and then add details afterwards. I hope what I’ve done will help. Good luck!
PS. It’s not letting me upload the modified blend… it just says “upload failed”