The idea of believing that every word of the bible is literally true is a very modern concept. The need for interpretation, for understanding of the changing meaning of words and practices, has been accepted since the early church fathers. It's not supposed to be easy - this is the crux of faith. If it were indisputably and provably true than you would not be capable of free will. Jesus rebuked Thomas for failing to believe even when presented with him being resurrected, pointing out that most will not have anything close to that level of truth.

There are different fundamental truths that you need to accept to "be Christian", it's been discussed for centuries - probably the most accepted would be the Nicene Creed.