WinDirStat is a nice tool for looking at disk usage.
https://windirstat.net/
Post some hard info such as screen shots or output from commands.
"the used and available totals don't make sense." Post the details. Electrons are cheap, post more and not less.
It is easy to copy text from a command window - google will no doubt tell you how:-)
Post the display from the Disk Management tool
https://www.howtogeek.com/101862/how...ther-software/
A side effect of a disk defragmenter is that it will display true disk usage. Nothing gets hidden. I have used MyDefrag. Just choose analyse.
Good luck.