Hmmm... Ok, what confuses you about Adam and Eve? They were the first people.
As for God working different in the Old Testament and why he doesn't do so today. My answer is this.
Romans 1:20 says, For since the creation of the world God's invisible qualities--his eternal power and divine nature--have been clearly seen, being understood from what has been made, so that men are without excuse.
That is a very important Bible verse. In the Old Testament God made himself known through defying laws of nature. Examples being Moses parting the Red Sea, Jonah living in the belly of a whale. These things for God would be easy because he's God. In the Old Testament God promised he would later send a Messiah. When Jesus came to be "the Messiah", he changed the way he made himself known. He made himself known through Jesus. He had Jesus performing miricales. He healed a paralyzed man. He raised Lazarus from the dead. He raised himself from the dead. God still makes himself known today as well he performs miricales maybe not as extreme as those in the Old Testament but he still does. Another thing to look at is prophecies in the Bible many of which have been fulfilled or are being fulfilled. That should confirm the validity of the Bible.
I still would say even if Jesus wrote the Bible himself people still wouldn't believe. The devil leads people astray.