I am receiving a message on my iPhone that 49.8 GB of storage out of my 50 GB total has been used. I want to delete files from iCloud, but it seems that they are linked to my hard drive. So if I delete from my iCloud Drive on my computer it disappears from my computer entirely. How do i clear up space in iCloud while retaining the files on my computer? I am using OS 10.13.6. Thanks.