Wyrmelin You might be able to get away with doing that by deleting the old tray folder and replacing it with the backup. Don't just combine them by dropping the old tray folder on The Sims 4 folder. Doing that might leave corrupted files. If you want to save any of the households in the corrupted save folder, check them first by starting a new game and drop them in. The game will usually tell you that a household or build is corrupted when you try to install it.
The thing is though; how did those items get corrupted? There is a good chance that they corrupted at the time they were saved to your Library. If that is the case, then the real issue may be that you save is corrupted. You can play a corrupted save for a while but sooner or later, it will fail completely and you lose everything. So, my suggestion for you is to save what households and builds you can and start over with a new save.
Hope this helps.