ideapad 720s

Hi guys, I've done desktop builds before, but never anything with laptops. I want to add another drive to my Ideapad 720S (15") - 81AC0008US, but I'm not quite sure how to go about it. In the little manual for the laptop is says, "M.2 SSD / PCIe 3.0 x 4" Does that mean I have 4 PCIe slots...

I bought my laptop used and it has been working great for about a month, but this afternoon some of the keys stopped working. I uninstalled the drivers and the device, reset my laptop, but the keys still don't work I read on multiple forums that it could be the cable rubbing against some metal...