You: Paul admits he is a liar in the following verse?
"For though I am free from all men, I have made myself a servant to all, that I might win the more; and to the Jews I became as a Jew, that I might win Jews; to those who are under the law, as under the law, that I might win those who are under the law; to those who are without the law as without law... that I might win those who are without law; to the weak I became weak, that I might win the weak. I have become all things to all men, that I might by all means save some."
Yes. Paul admits that he will say anything.
Paul claimed to be a "Jew among Jews," a "Pharisee among Pharisees," a former rabbinical student under Gamaliel, a former persecutor of Christians. I think he even claimed to be a member of the Sanhedrin.
I don't believe any of it.
Your ignorance doesn't make Paul a liar, sSimply because you don't believe him.