Lurkums, thanks in advance for trying to help.
I used the terminal command " Terminal is diskutil list" and the results are similar to yours with different volume sizes
The disk utility also shows a result like yours
I did not rebuild the Spotlight because I don't have any kind of problems with spotlight, also didn't quite understand how it would help in my situation
Regarding your last statement "You need to decide if this is 'real' used space or 'fake' used space before taking action" is where I need help:
1 - Need to verify if there is duplicate or fake space
2 - in case it is fake, how to delete it?
One more thing that I remember:
I have all my documents (photos included) in dropbox
After updating to OSx Catalina dropbox begun synchronising all the folders (photos library included) and I ran out of space
That's why I suspect of something.
The problem is I don't wanna mess with the library. I do not want do lose photos
Thank you