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Do you have working iPhoto application on your Mac ?
If you don't use Photos at all, then you can trash Photos library. Go to Pictures folder and trash the Photos library. Remember, this will delete entire Photos library. So backup it to an external drive and then delete it from your Mac. Empty Trash. This will bring back your space.
Then go to Applications folder and move Photos to desktop. If Photos is opening when you connect your Camera or phone, then you have to disable it in Photos. Refer this article --> http://osxdaily.com/2015/05/31/stop-photos-opening-automatically-mac-os-x/
You can also use this application OmniDiskSweeper to identify what is taking up all the space --> https://www.omnigroup.com/more
Let me know how it goes.