How old is Old Testament? As old as Sumerians?

The last book was written 800 years before Christ was born and we don't know when Job was written. Job was the first book written before Genesis. This is the book that has dinosaurs in it. It might have been written in 4500 B.C. or earlier on the side of a cave, or on old parchments. God is real and he is a God of miracles. One of his greatest miracles was preserving the Bible for us to read today.