230 GB deleted by iCloud Drive

ICloud Drive has hit me hard. It started with a corrupt external Time Machine drive. First I copied the 230 GB backup content onto the desktop of another MacBook. Next I reformatted the bad drive and started to copy the content back onto the Time Machine drive again. So far so good. But suddenly everything started to slow down, and iCloud Drive was complaining about being full. I looked into the options (at snail's speed) and discovered and option I had neither set nor seen before: that the content of Desktop and Documents was being copied automagically to iCloud Drive. I disabled the option – with the effect that every document on the desktop disappeared. Later I learned that this is normal, and the files can be found on iCloud Drive. Problem is that iCloud Drive was full! The 230 GB of backup copy had been reduced to 1 GB left on iCloud Drive! The rest, 229 GB, had been lost. Well, to add to the fun, its space has not been restored as free space. The MacBook now has 230 GB of no-man's land, not documents, not free space. To summarize, iCloud Drive has caused:

• 229 GB of backup files lost.

• 230 GB of disk space less.

• Computer painfully slow.

Help!