New Dell XPS 15 9520 Won't Power Off Please Advice

I am using the new dell xps 15 9520. Now when I don't use the computer for few minutes, it would go this screen where it is like a background picture and a quote under it where sometimes I press enter and it go straight to whatever I was doing, or I have to enter my windows password.

So when this occurred, I believe I clicked on that quote maybe. But then I clicked enter and it didn't work. It seemed to have frozen. I then went to hold power for few seconds and it doesn't do much except that freezing thing is now in the middle.

Can someone please tell me how I can fix this issue? My laptop is not plugged into an outlet. I do have that 2 in 1 usb and hdmi adapter connected to it. How do i power it off or restart? I have no idea what to do now.