Serious Haunting/Poltergeist Issues

Have any of you ever experienced a haunting/poltergeist?
If not, do you guys believe in them?

There's been a few things going on lately and I just don't really know how to handle it.

• Knocking on the door, no one home.
  
• Couldn't open door to leave, felt like someone was holding it on the other side.
  
• Heard a voice say the Latin equivalent to "exit".
  
• A random text document was created on my PC with the name "get out.txt" and it was blank.
  
• When I asked "why are you here" something rushed to the door, opened it, slammed it shut and did two LOUD knocks.