Welcome to Android Central! Does the keyboard connect via Bluetooth? What do you mean by "move the screen"--do you mean whenever you touch or swipe on the screen, the keyboard turns off? Bluetooth keyboards sometimes will "sleep" if you haven't typed anything on them for 5-10 seconds--once you start typing again, the keyboard wakes up (although this can lead to an annoying lag when you start typing again).
If the problem is very annoying, I'd bring it back to the store for an exchange or refund. Nextbooks aren't very high quality--you may want to look into more established manufacturers, like Samsung, Asus, Acer, Lenovo, LG, Sony, or Toshiba.