Christianity is mainly based on Paul writtings who are conflicting with Jesus teachings

 Paul believed that his vision proved that Jesus lived in heaven

 Paul was on his way to Damascus when he had a vision that changed his life: according to Galatians 1:16, God revealed his Son to him.

This are acording to the bible passed as christian tradition, and even if he existed how he can prove to others his words.

Link :

britannica

Paul contradicts himself :

2 Corinthians 13:7–9

8 For we cannot do anything against the truth, but only for the truth.

Link :

biblia

vs

Romans 3:7  

7 But if through my lie God’s truth abounds to his glory, iwhy am I still being condemned as a sinner?

Link :

biblia

The bible is filled with contradictions and vague words. Truth is a different word than lie. 

Paul contradicts the bible :

Psalm 101:7 

7  No one who practices deceit shall dwell in my house; no one who utters lies shall continue before my eyes.

Link :

biblia

Paul contradicts Jesus :

Ephesians 2:15

15 by abolishing the law of commandments expressed in ordinances, that he might create in himself one new man in place of the two, so making peace

biblia

vs

Matthew 5:17 

17 Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them.

Link :

biblia