Okay, I can only speculate but it sounds like you have a less-than-accurate grasp of what the Bible is. It's a collection of 66 books (give or take, depending on how you divide some and what Christian tradition we talk about).

That collection was written over a fairly lengthy time frame, depending on how early you date the earliest OT Books or elements of those books, but even critical scholars would on the whole date some material back at least 1000 BC.

Authorship of each text is usually discussed as a separate issue, because each book is a (distinct) entity that needs to be analysed and discussed on that basis.

So there is no 'overall' answer to your question, just a subset of smaller questions, "Who wrote X?" If you have a curiosity about particular books and would like /r/AskHistorians to discuss them, feel free to ask some follow-up questions.