I would make an appointment to see a psychiatrist. Sounds like you've got some serious problems there and if your actually hearing voices telling you they're going to kill you then you need to seek medical attention right away.
Did any of you all ever get overcome by demons or demonic things?
I have this problem. I have this demon that keeps talking to me in my head.
He keeps telling me he's going to kill me and take me to hell. I believe he almost did once.
I also see demons at night.
Do any of you have these kinds of problmes? If so, what do you do.
Get help. In all seriousness, make an appointment with a psychiatrist, as crazynonsense said, or get checked in a hospital if you're truly hearing voices.
As an aside, I personally doubt you're hearing demons as demons are actually kind spirits of wisdom and knowledge, not evil beings.
Exactly heimdallsman, they're actually great nice and kind spirits, so... they're either just messing around with you, or they don't like you, and you should reconcile you're past mistakes and differences that you caused. I had to. They will forgive you, leave you alone, or take you in as a son or disciple. It's up to you. Then again, you could just be having problems mentally, but I doubt it, but if so, the doctors can help you.