Greek, the Original Language of the New Testament

We got the New Testament in an "original" Greek. The Author was recently confronted with some claims that Greek was not its actual language of composition for the Christian Scriptures. Then he asked himself: "Were the autographs of the New Testament actually written in Greek or Hebrew, Aramaic, or whatever language or dialect was spoken by the Jews in Israel during the first century?" He investigated the matter and found enough reasonable evidence to come up with convincing conclusions. They are collected here, hoping they will be a satisfactory answer to those interested in this challenging question.