We have VERY LITTLE certainty that we have documented ALL of the most important things that Jesus said.
We have some confidence that MOST of what we think Jesus said was documented accurately, but there are obvious disagreements.
We have more than a few instances where Scripture WAS corrupted or changed and we know about it.
We do NOT know how many times Scripture was corrupted or changed and we do not know about it.
Written Scripture did not even exist in written form until at least 200 years after the death of the last Apostle. All early Christians were taught the Faith by Oral Tradition.
Then, when much of the Faith was reduced to writing (BY THE CATHOLIC CHURCH) it was all done by hand.
And then, it took a very long time until the Canon of the Bible was actually decided, and then Martin Luther tried to eliminate the Book of James and did eliminate several other Books, when he created the Protestant Bible.
We must trust Monks and Scribes to TRY and do a good job of hand copying written text for centuries, parchment and scrolls that did not last very long, and had to be copied again and again and again before the writings deteriorated completely.
How many errors to YOU make when posting online, where you can correct yourself rather quickly? How likely is it that the Scribes might have made a mistake or two every so often?
Faith
Faith is all we have.
We have LITTLE proof, in any scientific sense, that would give us 100% certainty that our translations were all accurate and that each time the documents were copied, they were copied correctly.
And again, thank a Catholic when you say the Lord's Prayer.
And remember that Catholics say it the correct way that Jesus intended.
If Scripture, which was written down and has been with us for 2,000+ years, is that inherently unreliable, then what on God’s green earth makes you think that *tradition* is any better?
Here, these will help you to better understand the reliability of the Bible we have:
Oral Tradition and the Gospels
Manuscript Evidence for Superior New Testament Reliability
The Formation of the New Testament Canon
Additionally, Luther did NOT remove any books from his German translation of the Bible. You can read more about this here:
If the word of God is as untrustworthy as you say it is, then NONE us of has a basis for the faith we have. God's word is immutable. He will ALWAYS preserve His word. Heaven and earth will pass away but the word of God will NEVER pass away.