HELP major issue DC when playing fullscreen

I get instantly dced from the game when i go full screen if I tab out i reconnect in the background. tab back in instant DC i can play windowed mode at the cost of beeing locked in 30 fps and 30 MS ping that feel more like 240 MS because it takes 0.5 sec for my caracter to move each time I initiate an action. pls help me i have no Idea what is going on.

I used the HRT multiple times now I checked my firewall everything is normal I alo did a full repair on the game uninstalled 2 times and Installed the game was working fine yesterday night. all i did was plug in a new monitor. which has nothing to do with internet connection or server connection.