Hello! my friends. been a lurker here for a while and finally need your help!

A year ago today i bought my first computer. i didnt build one cuz i wasnt really into it back then and only needed something to game/edit videos on a "budget" so i bought myself an Hp omen 188 110. Since then i have only upgraded RAM and a GPU. the specs are currently; GTX 1070 8gb, i5 8600k, 32gb RAM, HP motherboard, HP Power supply and 250 gb SSD with 1tb HDD

i NEED a better CPU to edit my 4K footage, i got a camera some time ago and its showing. i have upgraded RAM and already Use proxies with my SDD not even half full. i was thinking of upgrading to an i9 900k cuz i know the socket is the same (LG1511) BUT since i dont really know how old my build is since its a pre-built i can only imagine the motherboard isnt more than 2 years old? right?

i have no idea if it will support the I9, and when i googled the release date of the i9, everything was different and didnt really matter. 

im asking the pros here, plz help, if there is any other CPUs that will fit my board or finding out if my board will take the CPU