Horizontal lines when running games

[Stitch]

Today I've bought a new pc (ASUS) with the specs
Windows 10
NVidia Geforce 950m
Intel i3 5005U
I've installed the steam app and everything was fine. Then I installed Team Fortress 2 and when I ran the game it showed these horizontal lines that kept appearing and disappering in two different spots in the monitor. They were like "mirroring" a part of the monitor a couple inches below.
Then I uninstaled the game and used a second account of a friend of mine to try and play cs:go and the same happened. The same lines kept appearing!! What should I do? The pc is brand new and I really don´t know what to do, I'm really sad/mad because I thought I could finally start playing computer games... ) Please help me
(sorry for any mispelled word or bad gramar)

[76561198146916803]

I assume you must be talking about screen tearing. Enabling vsync will get rid of that. The down side is vsync also causes input lag making the mouse laggy which is a terrible idea for games like Counter Strike. The only way to get rid of tearing without using vsync is to get a 144hz monitor with or without g-sync (helps totally eliminate even the smallest amount and improve smoothness even more). Make sure your laptop can connect to another display or get a desktop gaming PC.

I just remembered some people cap their fps below the refresh. If the refresh is 60hz then cap it to 59. I don't know if that really works, but it's another free idea.

[Snapjak]

Like this?
https://en.wikipedia.org/wiki/Screen_tearing

Do what green suggests. Enable Vsync.