Well, I hate to disagree with you, but the early Christians were Jews, and it was common for almost all the Jewish synagogues to have at least a few copies/scrolls from books/scrolls of the OT, etc, because they were written on scrolls back then, etc, anyway, it was common for a lot of Jewish synagogues to have at least a few copies of some of the books of the OT that they both read and studied from on their holy day in both the Old and New Testaments times, etc. They were very big on writing and having things written down even way back then, etc, and scribes could be punished very much severely, and lose their position if they even miscopied or mistranslated even just one letter of one word, etc, so I think you need to do some more research and get some more facts there, as it sounds like you're getting your information strictly from social media or something like that, etc. And as far as the NT goes, and the books/scrolls written there, they kept the same tradition with them, etc, and copies that we have can be traced back to very nearly their time, etc, give or take about 40 to 60 years from the time of the Apostles or so, etc, and have changed very, very little since then, etc, so I think you are getting some very, very wrong information there, etc. Like I said, sounds like the kind of Biblical history denials I see going on in social media and things like that, etc, which are not based on any kind of facts at all, etc, but are just what people want to hear or say in order to dismiss history, or deny the Bible, etc.
Word of mouth did happen, and had to happen, etc, but if what people were saying wasn't the gospel, or didn't line up with what they had written down historically with the scrolls that were kept in churches or synagogues of both the old and new testaments at the time, etc, then those people usually didn't last long, etc, as the early churches tried to have at least some copies/scrolls from some of the books/Paul's letters, etc, from both the old and new testaments most usually historically, etc. And the places where the religious leaders learned or trained had a lot of them if not all of them, etc.
You need to get more correct information, and not trust sites like Facebook, and others first, etc.
Look into the earliest copies of both the old and new testaments online only using Google, etc. The dead sea scrolls might be good for you to look up as well or also, etc. Punishments for the scribes among Christian and Jewish traditions might be something else for you to look up also, etc. Anything having to do with the age of the written word among Christain and Jewish tradition/beliefs also, etc, and their strict rules regarding it over the ages, etc, but use Google, and not anything else, ok.
God Bless.