Hello once again!

Something struck me today that I had not thought much about before, but would love to have some help about. Jesus spoke in Aramaic, and I'm sure too his disciples. Why was it that the New Testament was mostly if not all written in Greek? Why was the Greek language chosen over Aramaic or any other language for that matter? Were the Gospels etc truly written by his disciples or rather were the writing passed down and translated to Greek through the adepts of his teaching lineage?

God bless!
OoA