Folder sync used in another connection

Hi! I updated owncloud to 2.11.1 version and when trying to add the desktop folder to sync I’m getting this message:
“Warning: the folder \Users\sandra\desktop is used in a folder sync connection! please pick another one!” My computer is macOS Mojave (10.14.6)
How should I fix it?
I am not very handy using terminal, so detailed instructions will be appreciated.

Many thanks!

Check here:
Desktop Frequently Asked Questions (FAQ) :: ownCloud Documentation

Thanks! but how can I know if these files are there: “.sync#HASH.db” or “.sync_#HASH.db” “sync_journal.db”, and in which folder? can I access them without using the terminal? or what should I type in the terminal to access and delete it…? apologies, I do not know programming language.
Many thanks!