Ubuntu and GTX960M

Hi

I have an Asus UX501V laptop with a GTX 960M graphics card and I am unable to get the Nvidia driver ruing. I know this topic has been discussed several times but none of the presented solutions worked for me. And after the third time of reloading my backup because I completely destroyed my system, I wanted to ask here, if someone could help me. Also in the past there where different solutions to get Optimus ruing with Ubuntu and I just don't know which solution is currently working and which driver I should use.

Currently I am ruing Ubuntu 14.04 but I also tried 16.04 with no luck. I have a single OS system, so just Ubuntu is installed on this machine. And I encrypted the system during Ubuntu installation.

Can anyone tell me how to install the Nvidia driver and also Cuda? Which driver version should I use? Which Ubuntu should I use, 14.04 or 16.04?

Thanks for the help,
ZO