I just changed my single user home directory to "/", can I return back?
Unless you have very specific technical reasons for doing so, then modifying MacOS's installation is unnecessary and may cause problems. There's no need to make separate partitions for users, or to move the default location of User accounts. 

As you have found out, the root level is read only in Catalina, and any non-OS files and folders will be moved to /Users/Shared when the OS is installed. 

If I were you, I would backup your data, boot to Recovery, remove any partitions, reinstall the OS, create a new user account, and then restore your data and apps to the correct intended locations.