Guild Wars 2

My nephew has the same exact computer as I do and plays the game without the graphic glitches. Can’t figure out why I get them and he doesn’t.

For about 2 weeks now I’ve been getting graphic glitches. Lines drawn out originating from pc or npc and out. I currently have graphics set on best appearance. I’ve also tried best performance and still have the lines. Blue and black lines that flash on and off.