Why do christians believe in god?

Mary would have been around the age of 13, not 30. God did show himself to people. Adam and Eve were the first and there are other records of it in the bible. Jesus is God, it's the whole trinity thing that is impossible for humans to understand. As for the wisemen, the bible doesn't say it's 3, and they aren't lunatics they were astrologers or astronomers... I can't remember which is the one that studies the stars. And lastly, the majority of the people didn't believe him, that is why he was crucified. So why do I believe? Look a demon in the eye and tell me you don't believe that there is a God who can defeat it. Most people will call me crazy but I've seen a demon, heard the voice of God and Satan as well, felt the Holy Spirit and all before it was explained to me what it should be like and yet it still lines up with other peoples experiences.