Bought a PC with SSD which filled up as soon as loading games from steam etc. Now trying to migrate off and I can not use the windows "move" function for folders like APPDATA local or roaming because of long files names. I simply can not get enough off of C: to run the machine reliably.
I would remove the SSD and suggest you buy a larger hard drive and reinstall windows. You can always put that hard drive back in or get an external enclosure so you can get access to your files.
If you are using Windows 10 you can change your settings to store your apps, documents, etc. on the HDD. If apps are already installed you may have to uninstall them, then change the settings and re-install the apps. See: www.windowscentral.com/how-manage-file-storage-windows-10