X51 R1, upgrade or new build?

Hi, I have an Alienware x51 r1 for the last number of years. I have used it heavily up until about 2 years ago when I moved on to a laptop. I want to go back into using it but the reason I stopped using it was due to it becoming very very slow. I am not a Pro on what goes into computers, what’s needed for them  to be fast etc. I want to use my Alienware for gaming, editing and multitasking. I know this might be a very general question but what should I do to help upgrade my PC as it’s prob 6/7 years old at this stage and could do with a refresh, or am I better to simply build a new pc and start from scratch. I have a screenshot of the PC specs below. Please don’t hesitate to respond. Any help would be very much appreciated!