LAN issues i've never experianced before :/

The title sums it up, the problem is that once me and my friend setup a lan room which works perfectly and fast. We both have really good net speeds, but once we start the game oh boy, it stutters beyond imagination. Actions take about 3-4 seconds before any response. I've tried to search online for any fixes but all it came down to is; deal with it :( It's the game of my childhood and i really dont want to refund it but if this continues i doesn't leave me a choice. We play alot of lan together and this is the first time this happens.

specs for people who will ask:

intel 6700k gtx 1070 16gb ram

i play the game on max settings, and sorry for bad englando :)