cant see objects with walls down

@neelus-neeltje  I'm guessing that the objects don't reappear when you put the walls up.  The objects you mentioned are of course supposed to disappear when a wall isn't showing, but reappear when the wall is up again.  I've had this issue myself a few times, but I almost always saw it right after my sims had moved to a new lot.  In each case, I quit and reloaded a save from before they moved, and the problem didn't recur.

So I'm wondering if this happens on every lot you try, or just one or two that you normally use.  Is this in an existing save or new ones as well?  Even though you uninstalled, if you didn't delete your game folder in Documents, you would still have your old saves, and perhaps some old corrupted file.  So pull the entire TS3 folder out of Documents and onto your desktop; a new one will spawn the next time you launch the game.  Load some premade family and see if the problem still occurs.  If not, maybe it was random, or there is something weird about the lot you've been playing.

If the problem is gone, you can copy your current saves and other content from your old game folder to your new one.  Here's a list of all the files in that folder, along with explanations of what they are and which ones you might want to keep:

https://sims3.crinrict.com/en/2011/01/faq-user-files.html

If the issue only happens in your current game, but you don't want to start over or move your sims, you can try bulldozing and replacing the house.  Go to Edit Town, evict your family, save the house to the bin, bulldoze the lot, replace it with its bin copy, and move your family back in.  If you do this all in one Edit Town session, without saving and replacing your sims, they'll keep their jobs and relationships but lose their promised wishes and opportunities.  Hopefully the objects on the walls will show up again, and they won't disappear this time around.  But if this doesn't work, or you don't like some other side effect, you can quit without saving.