Genesis is the understanding of God by the ancient Hebrews. It's there oral tradition handed down and finally made into a book by Moses and his advisors. It's ancient man's understanding of God and the building of a religion. It does look like some of the early stories are taken from Sumerian and Egyptians sources adding Hebrew philosophy to them. Abraham was a Sumerian. They were building there understanding of God and not all of it is perfect or explainable. It evolved from out door animal sacrifices to a tent temple to a building temple. The Hebrews weren't perfect and there understanding of God at times isn't perfect. But at the time in the known world they recognised more of the truth of God. So God revealed himself more to them and of course this brought the saviour Jesus through them. Knowing that the bible isn't perfect, doesn't take away the bible but authenticates it.