Please help the number 5 doesn't stop typing

@glenn680 sounds like a stuck key or broken key switch. Try using a USB keyboard and see if that helps. Also, try a can of "compressed air" and blow out the debris dust from beneath the #5 keys. See if that clears it up.

If not, consider replacing your keyboard. Now here comes the tough part. The keyboard is considered part of the "Front Case". It is held in place by what looks like plastic rivets. You would have to remove those, clean it up and then glue a new keyboard in pace.

All of that is very time consuming and makes it difficult to replace the keyboard on its own. Check on here for the Samsung repair video. Of course, you can also use the NP750XGL Repair Guide

Now, make sure that you do no longer have any warranty etc., on this laptop. If you do, call Samsung and let them repair it.