input lag/delay

I'm a PC gamer but i wanted to play console with some friends on rainbow six siege and wanted to play keyboard & mouse so i got the keymander 2, all the reviews said it had 0 delay/input lag but when i play there is a noticable delay, how do i fix? my dpi is 6400 on mouse and 6000 on app i have my polling rate on 125 hz aswell, my mouse is a glorious model o wireless and my keyboard is a ducky one 2 mini