I found that the problem was Microsoft Office (big surprise). It had library files that were almost 87 GB, and for what?

I had to uninstall the programs, go into the Library files and delete them. The way to completely uninstall MS Office for Mac is here: https://support.office.com/en-us/article/Uninstall-Office-2016-for-Mac-eefa1199-5b58-43af-8a3d-b73dc1a8cae3

Also try to clear out the .trashes folder:

http://superuser.com/questions/728709/how-to-delete-trashes-on-ntfs-drive-on-mac

I found that the problem was Microsoft Office (big surprise). It had library files that were almost 87 GB, and for what?

I had to uninstall the programs, go into the Library files and delete them. The way to completely uninstall MS Office for Mac is here: https://support.office.com/en-us/article/Uninstall-Office-2016-for-Mac-eefa1199-5b58-43af-8a3d-b73dc1a8cae3

Also try to clear out the .trashes folder:

https://superuser.com/questions/728709/how-to-delete-trashes-on-ntfs-drive-on-mac