I think that while JN14:16 and JN 16:13 is all well and fine, one needs to look at JN 21:25 where is says “There are still many other things that Jesus did, yet if they were written about in detail, I doubt there would be room enough in the entire world to hold the books to record them.” What this tell me is that there were many things that Jesus said and did and taught that was not written down. In the first early years after the resurrection, there was little thought given to writing down a Christian library. Some of this was undoubtedly due to the example of the Lord Himself, who like the rabbis of the time, taught by the spoke word, which in turn was remembered and discussed by disciples. There was no need for writing while the Apostles were still alive to clarify or verify anything uncertain.
What Jesus commanded and meant the Apostles to do was precisely what He had done Himself, deliver the Word of God to the people by the living voice, convince, persuade, instruct, convert them by addressing themselves face to face to living men and women; not entrust their message to a book which might perish and be destroyed and be misunderstood and misinterpreted and corrupted, but adopt the more safe and natural way of present the truth to them by word of mouth and the training others to do the same after they themselves were gone and so, by a living tradition, preserving and handing down the Word of God, as they had received it, to all generations.
The Gospels are incomplete and fragmentary, giving us certainly the most important things to know about our Savior's earthly life, but still not telling us all we might know or much we do know in fact and understand better through the teaching of the Catholic Church, which has preserved traditions handed down since the time of the Apostles, from generation to generation. what is contained in what we call the New Testament were called into existence at various times to meet pressing needs and circumstances, were addressed to particular individuals and communities in various places and not to the Catholic Church at large. The writing that would be called sacred Scripture, the New Testament was the furthest thing from the minds of the Apostles and writers, they did not or never thought that what they wrote would be put into a one volume and made to do the duty as a complete and all sufficient statement of Christian faith and morals; this in no way undervalues the written Word of God or placing it on a level inferior to what it deserves, but shows the position it was meant to occupy in the economy of the Christian Church; it was written by the Church; it belongs to the Church, and it is her office, therefore, to declare what it means. It is intended for instruction, meditation, spiritual reading, encouragement, devotion, and also serves as proof and testimony of the Church's doctrines an divine authority; but as a complete exclusive guide to heaven in the hands of every man, this it never was and never intended to be. The Church came before the New Testament and supplements the oral teachings and traditions of the Catholic Church.