Is the Catholic Church altering the Gospels and the teachings of Jesus?

The Catholic Church seems to be adding things to the Gospels which were never written down by the Apostles. For example, where in the Gospels is it mentioned that the Pope is the representative of God in the human world? Or that it is alright to kill non-believers of Jesus Christ? Or that it is okay to wage war in the name of God? I don't think Jesus ever said those things.