LAG SPIKES

I got an i5 7600k gtx1070 8gb ram 3200 mhz 1 tb 1 ssd 256gb why i got lag? i run in low settings i got too lag in extreme same , i mean i got that lag only on online session i don t know how to fix it
I GOT AN GOOD INTERNET TOO AND STILL LAG
IN SOLO ALL IS GOOD, NOA LAG all is perfect but in online i got lag !! not fps drops!!!