What part of the New Testament can be trusted? Each gospel tells a slightly different story.
It's true that each gospel tells a slightly different story , at least that's true of the synoptic gospels, Matthew, Mark, and Luke, with somewhat different words by Jesus, and at different parts of the story sometimes. However the essential sense of what He said is conveyed.
John is a different kettle of fish. He says many things not in the other gospels, like, for instance how high His station is, which many Christians have interpreted to Him saying He is God. The events are different in many cases. There is, of course still the crucifixion, and also the resurrection. The knowledge of the disciples of what His station is comes much earlier in that gospel.
I asked my father, who was a Quaker minister, which version of when the disciples knew was most trustworthy, and he said the synoptic gospels. The Baha'i Writings seem to say the same thing. It is accepted by scholars that John was written later than the others. Also Matthew and Luke were based on the template of Mark, with another source called Q added in.
I believe that the gospel of John was written from a different source to give a different point of view from the others, to add supplemental material.
Then there's Paul. Most of the NT is his letters. He wasn't the messenger, but his writings are declared to be the "Word of God" by Christians. Then who wrote Hebrews?
There are different opinions from Baha'is, but I think sometimes Paul was inspired by the Holy Spirit and sometimes not. He was a basically a good person, though not perfect. For instance he was insistent on his own point of view to the point where he said:
But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed.
Paul, "The Epistle of Paul the Apostle to the Galatians - επιστολή προς τους Γαλάτες", 1:8
As we said before, so say I now again, if any man preach any other gospel unto you than that ye have received, let him be accursed.
Paul, "The Epistle of Paul the Apostle to the Galatians - επιστολή προς τους Γαλάτες", 1:9
This one statement helped lead to centuries of intolerance. It also didn't help that Constantine insisted 3 centuries later that Christians adopt one view, and call all else heresy. That was his way to unify the Roman empire.
Some letters purported to be from Paul were not by him but from anonymous people that used his name to advance their point of view.
No one knows who wrote Hebrews.