So lets take a moment to step back a bit.

A lot of modern Christians take the first few books as mostly being creation myth. As in it's a story made thousands of years ago to explain things, not hard and fast truth. Stories meant to inspire and make the world easy to understand.

Most Christians consider the parts afterwards to be more factually based, though even then it depends on the church and individual which parts and how much so.

The part to also remember, and in fact related to your last sentence, is that the books were written by differing authors sometimes hundreds of years apart. The bible is basically an anthology of related works from people who believed in the the same god(and to some degree, potentially intermarrying similar religions in the area). They all believed in the same god, and combined the literature into a single book. So, really, it's not one book. It's dozens, written by different authors for different purposes aimed at different people/cultures.