Backspace, space, enter keys not working half the time

Hello, I have a Dell computer with the latest windows on it. Half the time the space bar doesn't work. And most if not all the time the backspace and one of my enter keys don't work. No matter how hard, long or how many times I press it, it will not work. Very rarely it will work but that is only if my computer is on for a very long time. Please help. I am a college student and it makes it VERY hard for me to get school work done efficiently.