There is no contradiction in true Jain scripture, but there are contradictions in the present time. The reason being different people took meanings of different words differently unintentionally or intentionally. Some people have even changed the words of the scriptures. So you cannot follow them safely. But that doesn’t mean that you shouldn’t follow any. Try and find what you think is the best.
I would like to correct you that most of the scriptures are the written form of the vani of kevalgyani bhagwaan, and his knowledge was perfect.
I think you are talking about Christianity. Jesus was born in 4 B.C. only, while our religion has no beginning and no end. If you want proof of existence of Lord Aadinath or Lord Parshvanath, you can check this: https://qr.ae/TUyscC
But if take a deep drive into jain scriptures, you can get the true knowledge.