@TJG951 Are you still having issues saving and/or loading existing saves? This could be related to drive space, but there are plenty of other causes. Let me know if you'd like to troubleshoot that issue specifically.
In case it's not totally clear, there are a few different ways you can move Sims 4 files away from C, if you'd like.
- You can install the game's program files on a separate drive, or move them there using Origin. If you use Origin to move the files, or you uninstall/reinstall, the game should work fine.
- You can redirect Documents in its entirety to another drive. This is supported by Windows (see @kreatora's link) and should not cause any issues with saving or retrieving user data.
- You can move only the Sims 4 user data folder from within Documents to a separate drive, using a symbolic link. This is not overly complicated either, nor particularly risky. If you do it wrong, you might delete your Sims 4 folder (which is why it's good to have a backup), but that's about it.
If you'd like help with any of these steps, please feel free to ask.