everytime i go to do my mission or anything else the regards with "Fire to start" or whatever it is , i get stuck on that screen, nothing happens at all even when i click to shoot. I can hear the background noise of the enviorment but thats about it. Can anyone help me?

"Nothing happens" For how long do you wait after you press the fire button a couple of times? Sometimes it just needs to load a little bit more then usual.

I get a slight lag on the same screen, but after mashing the mouse button half a dozen times it eventually works.

Can you get in to the mission at all?