David, thank you for the Christmas wishes. I had a lovely Christmas, and I hope yours was as well.
As for turning off the storage of documents in the Cloud, here is an excellent article for you, with pictures, of how to do that:
https://osxdaily.com/2020/07/18/how-enable-disbale-optimize-mac-storage/
Note that in the article all they suggested was to turn off "Optimize Mac Storage." You may also need to click on the "Options" button beside the iCloud Drive entry also shown in the images of that article and then un-check "Desktop & Document Folders" if it is checked there.
Start by making a backup of the drive. Check that the backup is good and then you are ready to start this process.
First, however, consider this: Theoretically, when you turn off the optimization function, it should offer you the opportunity to download all of the documents currently there. As the article says, that can be a lengthy process, depending on how much has been moved there over time. What I would do, personally, is that I would download those documents and other items manually, just to be absolutely sure I had them. But if you do decide to download them manually, they cannot be put in Documents or Desktop, as those two folders will be messed with again by the turning off of the optimization of storage. So what I would do is to copy them from iCloud to either an external drive (if I had one), or to some other folder if I have space on my internal drive. I'd name them something like "Downloaded Documents Folder" or "Downloaded Desktop Folder" or some such. Those folders should NOT be on the Desktop or inside the Documents Folder of your home folder. Put them at the same level as Desktop and Documents. Note that if you have Photos stored in the cloud you will want to download all of those images as well. They all just go into the Photos database, so that is OK.
Now when you follow the article and turn off Optimization, I think you are presented with an option to download everything stored in the cloud. If you did that manually, you don't have to do it again. If you decide to do it again, the system should re-create your Desktop and Documents folders and fill them with what was in the cloud. If you don't download again, the system will create new Desktop and Documents folders and leave them empty. If you choose to go the "don't" path because you downloaded them manually, at this point you can copy or move all of the files from the "Downloaded" folders to these two new empty folders and you are back to where you want to be. Once everything is where you want, you can do whatever you want with the "Downloaded" folders, keep them or trash them. If you choose the "do download" option when offered it, double check that everything you want ended up in Desktop and Documents and then you can do whatever you want with the "Downloaded" versions of those folders.
Depending on your internet speeds and the amount of stuff you have in the cloud, it could be a lengthy process to complete this transfer, so you will need to be patient. And remember that the Desktop you see on the screen is a representation of what is in the Desktop folder on the drive, so don't try to move things from the folder to the screen because they are already there.
