Where are the original Aramaic manuscripts?
Sometimes I think people imagine the Apostles all had scrolls and ink with them every time Jesus spoke and that it was their copious notes that became the gospels. But we know that isn't how it worked. The Gospels were written decades after the events and were the writings of those who were eyewitnesses of what happened but who, through the leading and inspiration of the Holy Spirit, wrote the EXACT words God intended be preserved forever. So, Jesus probably DID speak to the multitudes in Aramaic or Hebrew - depending upon the audience. He may even have said some things in Greek from time to time. But, the point is that no matter what language Jesus SPOKE, what he said was written in Greek, copied, disseminated and preserved for us all.
That is why some Hebrew idioms might sound different in Greek or why a direct Aramaic phrase was written with the Greek for emphasis. It doesn't prove that we somehow lost the "originals" in a different language and we're "stuck" with Greek. Only that what we DO have is what God meant for us to have and it IS and REMAINS God's word.