The man who shocked the world of both those that believed in God and those that didn't. He lived over 2000 years ago and still changes the hearts of people today. What's there to believe about him and why do I.
What is Christianity
Christianity is a (true) story about a God who created a beautiful world, with creatures to whom he gave the power to make it's beauty shine or to ruin it (which they did). A story about you and me, who live in a vast world, with the power and mission to make it a little bit more beautiful, which we do not always do. As a result we can't get to live with him anymore, but should go to hell. Sorry, there's no nice way of saying it. The story doesn't end there though, because he set out to make things right for us and sent his only son, Jesus, to die at a cross. He conquered death, went back to heaven and will one day come back to bring us home if we follow him. Will we? It might cost us everything. It certainly did for him.
Why do I believe
Because I know he exists, and he is who he claims to be.
I can see it in many small things, some are very hard or impossible to name. Things like when a hurt friend gets hope again, or when God is so near that nothing else matters, or those moments that he speaks through me. It's visible in the way people tend to hate Israel and not tell the truth in that ever ongoing war. I can also see it in how the Bible is correct in amazingly small details. For example the efficiency of the old testimony laws or the archeological discoveries concerning the red sea crossing. Those parts where the Bible goes crazy, counter intuitive, unpredictable and true. Just like the world around me.