How to avoid sync for already existing folders and files in client PC

I’m less than a newbie. Please be kind. :grinning:
I’m using nexcloud from a server provider, my question is: If I create a new user that has access to already running group folders, can I copy the group folders current content using a pen drive from another PC in order to avoid sync several GB of data?
I tried to create a new user, copyied current group folders and files from another PC and configured the populated client local folder, but nexcloud start updating (overwriting) everything from scratch (98GB, 12 hours with my slow bandwith connection).

Thank you for your help!