Assuming we have any confidence at all that the Gospels and Epistles we have as the canon of the NT are speaking to us of real event, (I do by the way)then it's because we have the nearest thing to what the writers actually wrote instead of made up nonsense from the 19th and 20th Protestant West written to advance a 500 year old heretical agenda.
You have no manuscripts that are not available to everyone else so “ the nearest thing to what the writers actually wrote” is available to all translators.
If you wish to argue with the how of translation that’s another matter but speaking Greek provides you with no special theological insight on the meaning of the Scriptures.
The Jews say pretty much the same thing with regard the Christian interpretation of the Old Testament, Kolo mou. They insist that without knowing the Oral Torah, one cannot properly interpret the Written Torah.