accidentally turned on sync files to apple icloud - how to stop and reverse it

In Finder>settings, I foolishly clicked on Sync Desktop & Documents folders. I didn't actually click the box - if you click anywhere close to that line in the window, it will automatically check the box for you.

I immediately unclicked the box and clicked Turn Off on the pop-up.

Unfortunately, that doesn't stop the process. I can see the MacBook Air is trying to move folders and files to iCloud. But I don't have anywhere near the storage required in iCloud (300G of files on MacBook Air vs 50G storage in iCloud).

1) How can I stop the MacBook for trying to move the files? I can see the progress clock - it is trying to move them.

2) How can I reverse the whole thing and put all my Desktop & Documents folders back on to the MacBook Air and remove them from iCloud? I don't know which files from which locations it has already moved.

Please give me step by step instructions - I'm not proficient.

Thanks