Hello
If you uninstall and reinstall your game you will not lose your save games that are in your saves folder or your library gallery items that are in your tray folder, that are in your sims 4 folder. It is best though to make a backup copy of your Documents-Electronic Arts -Sims 4 folder before uninstalling , and place it on an external drive or another part of the computer.
Is a mod not working in your game? If it isn’t working, try checking on the download site to see if there is an updated version.