Before we read anymore of Luke, let's go over what the Old and New Testaments are.
The Old Testament is scripture that both Christians and Jews consider holy. It was written by multiple people from c.1400 BC to 400 BC. It has 39 books. The different books have different styles: law, history, proverbs, philosophy, song lyrics, prayers, prophecies, poetry.
The New Testament is written by followers of Jesus Christ, from c.40 AD to 80 AD. These writers frequently quote the Old Testament, believing that it foretold things about Jesus - things that they saw come true, or heard about. The New Testament has 27 books: 5 story books, 21 letters, and 1 apocryphal book (an old genre).
Both Testaments together are the Christian Bible.
Just a thought: I think that ancient Judaism (in it's purist form) and Christianity (in it's purist form) are the same religion.