Does God exist?

Does God exist? I've been wondering this question all this while. Maybe it is true? Or maybe it is just a myth? If God does not exist, then why until now everyone is still praying? I'm so confused...

Alright, let's go to the next step. If i am the professor, i'll say this:
Does cold exist? -Yes. Because when there's no more hot, something have to replace the hot which is cold. This is why cold exist. Then God made human to realise that cold appear when there's absence of hot. Everything happens for a reason.
Does darkness exist? -Yes. Same thing. When light is gone, God use darkness to replace light. Everything happens for a reason.
Does evil exist? -Yes. Why? Because, when there's good, there's a bad. Everything has it's opposide. If there's God, then there is also devil. God tried to make humans do good deeds while devil is the opposide. They make human to do evil for some reasons (i'm not a christian, so i don't know much about all these stuff. But i know some of these things because some of my friends and relatives are christian.)So that they could rule the world? I think so.Well, for what you can see nowdays devil is ruling the world. Take a good look around you. And once again, things happen for a reason.

*I get this video from my friend who shared it in Facebook.