[ubuntu] Intel HD graphics 520 driver

Hello.
I had an exteal hard with Ubuntu 14.04 ruing on it. I was using it happily, until I bought a new laptop. So I coected to new one and I was working, then I recognized my cpu is on high usage, It was compiz problem. After that I checked my graphic and I found my graphic card is not installed. While I have a NVidia gtx 950m graphic card, so I decided to install this one driver. I did, and I restarted the system. Login page appear, I entered the password and it logged in, but the desktop doesn't show, and it is just the purple Ubuntu wallpaper and nothing more.
I tried to reinstall driver with gnome terminal (alt+ctrl+f1 in login page). But for any command it asks the password, when I enter my password it says login incorrect whereas I enter same password always and was working before this.
So how can I fix this?

a friend told me I should reinstall OS. I installed 16.04 on hyper v, but exactly same problem. What should I do now?

thank you all!