Guild Wars 2

I’m having the problem of random environments popping in and out of existence and blue streaks as well as red outlined white diamonds popping up on my screen. it’s so bad I can’t play the game. Sometimes I’ll be running around and I’ll be attacked by nothing and then a centaur or something flicker in and then out of sight and I can’t fight back. I’ve tried un-installing and re-installing the game and that didn’t fix it so.. I have no idea what to do now. Please fix this soon; I’d like to play my game over my break..