Thin lines on screen, freezes bottom half, flickering.
So basically half of my screen flickers faintly and, sometimes when I'm playing a game it has thin black horizontal lines, sometimes with green bits. This bit I have seen sometimes, and I could live with it, but the most annoying bit is when sometimes, the bottom half of the screen that flickers, freezes and is transparent so you can see the current display, but that half of the display from a few seconds earlier. I have no clue what it is or how to fix it. I don't know if it is relevant, but the game I was playing is Assassin's Creed IV: Black Flag, from steam, and I downloaded it a the same day this started, so it might be that but I don't know. I have a few pictures of it happening if they are needed, but I don't think I can put pictures in this description.
Just want to know how to fix it, thanks in advance.