Getting out of iCloud
How do I stop using iCloud? I suddenly, after years of not using it, getting notifications that I am running out of space. For the past 2 days, my modem has been transferring my info into the cloud, and I don't want ANY of it there!
If I try to log out, it takes away the information from my desktop calendar and I need that info to stay on the iMac.
HELP!
iMac 27", macOS 10.13