Nowhere in the Bible does it say they are word for word. The Quran says it was dictated word for word, thats verbal inspiration. But the Bible says holy men were moved by the spirit, thought inspiration. Men put it down in their own words.
My trust in the scripture is not based on it being word for word, but in it being inspired by God.
People had better memories in those days. Studies have been done about it. And the dicsiples were there to listen to Jesus praying in John 17.
Just an FYI - this aspect of memory and the gospels has been researched by some pretty thoroughly..