Dinosaurs up until very recently (like a century and a half) were known as dragons, and when people encountered them that's what they were called. There are creatures described in the Bible that sound very much like what we now call dinosaurs. Am I positive that a man ever saw a dinosaur? I'm not sure of anything, but if you believe the Bible then yes. Dragons are fequently mentioned in the Bible.
Where did God come from is the wrong question, as Christians believe he is eternal. He was uncreated and has always been and will always just be according to Christians. It is impossible for mortal minds to wrap their heads around it, but the interesting belief of the Christians is that since nothing could have happened without a first cause, and no matter HOW FAR you go back, back to the singularity, what caused that? Not matter how far you go back, THAT TOO would have had to have been caused by something else, so only an ETERNAL BEING being responsible for all creation is the only thing that makes sense.