furby_irl Please list the locations of the symlinks you currently have and where they point to. I'd like the full paths for each one as well as what is inside the redirected folders.
The error in CMD is because there was already a file or folder with the same name in the same location as where you told it to create the symlink. That's not a surprise if you already have some kind of junction there, or if you started the game again and thereby created a new Sims 4 folder or any subfolder inside.
If you'd rather start from scratch, please see this guide:
📓[GUIDE] [PC] Choosing where Sims 4 data is stored | EA Forums - 12598500
Moving the game's program files does technically require reinstalling. However, there's a shortcut, detailed in the guide, that works some of the time.