You seem to have dismissed the OT.
The Church alone got the divine authority to sort out the true word of God over three centuries. Suggest you read F.F. Bruce's The Canon of Scripture for how the NT was decided.
Why don’t you simply take the Evangelist John at his word, and instead of trying tp play internet theologian, when all your leading Protestant theologians have studied and taught the Bible for years and have seen the light and converted to Catholicism?
Erroneous and error filled statement on your part....all leading Protestant theologians have converted to Catholicism.
No one has denied there was oral teaching. What is denied is Rome's interpretation of this teaching.
Despite being asked many times, Rome cannot provide us with an authoritative listing of what this oral teaching was.
Christianity can point out what it is not though.
And I see you still cannot refute the contradictions between Roman Catholicism and Scripture on Mary as you've now moved the goalposts to shift the conversation to how we got the NT.
The Bible is the “selected” words of God that made itself into print. The Church “interpreted” what was true and untrue from hundreds and hundreds of manuscripts and papyrus fragments.
This interpretation was inspired by Divine guidance did not vanish after the first 1300 years with heretical Lutheranism that opened the door to the Billy Grahams; Joel Osteens; Jeremiah Wrights, and everybody’s grandmother and neighborhood self-appointed pastor to crack open the Bible, overlook the oral tradition as mentioned by John the Evangelist; and instead offer their own “individual” reading of literal text as being authentic interpretation.
This is the stuff that is fed to low-information Protestants, while leading Protestant theologians, scholars, teachers, and preachers have after years and a lifetime of study discarded this rot, and have converted to Catholicism.