I'm new to linux so I don't quite understand what i did exactly. I wanted to update my Nvidia drivers and I read somewhere that I can do that from the terminal with " sudo service lightdm stop". Some text appeared on the screen and nothing happened, the screen like froze. I waited for some time then decided to restart the laptop, and from then on every time it gets to the desktop the screen goes like crazy and the screen freezes. I restarted and entered the terminal before going to desktop, used sudo service lightdm start or restart, texts appeared again then a black screen. Can someone explain to me what happened exactly and how to fix this ? Also how can I download the newest Nvidia drivers ?