Are you sure you have an actual GTX 1080 ti? If you bought from Wish.com or a similar site you might have gotten a fake graphics card. I just can't imagine a GTX 1080 ti performing that bad even with your CPU and RAM. Try to run a 3Dmark firestrike test to see what score you get.
https://store.steampowered.com/app/223850/3DMark/ download demo.