If you're going to make an assertion, you need to be prepared to substantiate it:
"It is generally agreed that Jesus and his disciples primarily spoke Aramaic, the common language of Judea in the first century AD, most likely a Galilean dialect distinguishable from that of Jerusalem.[1] The towns of Nazareth and Capernaum in Galilee, where Jesus spent most of his time, were Aramaic-speaking communities.[2]" Wiki
And if you're not a fan of Wikipedia, I can find you a whole lot of other sources saying pretty much the same thing.
What language Jesus was speaking is irrelevant in that the Holy Spirit inspired the New Testament to be written in Greek. Do you honestly think that the Holy Spirit didn't know what words to use to convey His meaning?
It's the meaning that is conveyed that is under discussion. The Holy Spirit inspired the words of John 1:42 as well. Some are contending that the use of "petros" in Matt. 16:18 means "upon this rock" isn't referring to Peter. Taking Scripture as a whole, that Jesus in John 1:42 says that Simon will be called "Cephas" (rock) is a good cross-reference to know that "this rock" does refer to Peter.
Ok.
Koine Greek (/ˈkɔɪniː/ or /ˈkɔɪneɪ/; from κοινός/κοινή "common", also known as Alexandrian dialect, common Attic or Hellenistic Greek) was the common supra-regional form of Greek spoken and written during Hellenistic and Roman antiquity. It developed through the spread of Greek following the conquests of Alexander the Great in the 4th century BC, and served as the common lingua franca of much of the Mediterranean region and the Middle East during the following centuries. [Bubenik, V. (2007). "The rise of Koiné". In A. F. Christidis. A history of Ancient Greek: from the beginnings to late antiquity. Cambridge: University Press. pp. 342–345.]
The mainstream consensus is that the New Testament was written in a form of Koine Greek ,which was the common language of the Eastern Mediterranean from the Conquests of Alexander the Great (335–323 BC) until the evolution of Byzantine Greek [Wenham The elements of New Testament Greek -p xxv Jeremy Duff, John William Wenham - 2005] [Daniel B. Wallace Greek Grammar Beyond the Basics: An Exegetical Syntax of the New Testament 1997]
Greek was the most ideally adapted linguistic medium for the World-Wide communication of the Gospel in the entire region of the eastern Mediterranean, Egypt and the Near East. [Archer, Gleason L. 1975. Zondervan Pictorial Encyclopedia of the Bible. Vol. 3. Merrill C. Tenney, ed. Grand Rapids, MI: Zondervan.]