Changing language of the game with reinstallation

@H8H8H  As you've seen, changing the game's language doesn't affect any saves you've already created, and there's no way to edit world or neighborhood names within the game.  You may be able to do it with Sims4Studio though—at least, google thinks so.  I haven't tested, so I have no idea whether it still works, but you could always experiment on a backup copy of one of your saves.

Your new saves should have English names even if you don't reinstall the game.  At the very least, test it out first, as in, start a new save, before going through the trouble of uninstalling and reinstalling.

For your existing saves, if you save your households and builds to the in-game library, the associated files will all be in the Tray folder.  I'd still keep the old saves on hand in case you need them later, but you won't need their data when you're placing the sims and lots into your new saves.

For any other user data you might want to preserve, please see this guide:

https://sims4.crinrict.com/eng/2014/09/user-files-explained/