New to gaming pcs and don’t know much about the specs. Would y’all kindly help me out? Also if I’m buying used from a reputable dealer, what should I look out for?

Looking to play Fortnite, league of legends, and use as a work computer. Currently on a 12 year old Xbox ????

Specs:

Zotac 3070ti gpu I9 9900k cpu w AIO Lian Li Bauer case 64gb g skill ram As rock z390 steel legend mobo 850w psu Windows 10 pro installed 1 TB m.2 nvme 4tb ssd