Can't figure out what is taking up so much space
To try and locate which files and directories are consuming the most disk space on your Mac, I'd recommend running OmniDiskSweeper. You can run it off of the DMG just fine. Select your hard drive and let it run and it'll list in descending order where the greatest disk usage is.

OmniDiskSweeper: https://www.omnigroup.com/download/latest/OmniDiskSweeper

From there you should hopefully be able to free up some space.

Hope this helps you!