WHY AM I LAGGING

Ok hey guys. I just paid 1550$ for a ''gaming computer'' that can't even run LoL at very high. I'd like to now if this is my pc or the game. I have a EVGA GeForce GTX 1060 3gb. i7 7700 CPU 3.60 ghz. 8 of ram. motherboard is bazooka b250M from MSI. I feel liek this should easily run LoL at very high.. It's a new computer. Thanks for helping me. This is mainly in late game. I have arround 100 FPS but feel like i have a freeze like every 1-2 seconds :/