See this page to explore the evidence, e.g.:
This is relevant because:
A) Knowing these bits of Jesus’s biography (geneology, status, sayings/teachings, ethical conduct, miracles, crucifixion details etc.) just is what it means for Paul to know Jesus biography generally.
B) Each known detail implies Paul has source(s) of knowledge on Jesus biography (and so likely knows more than he reports.)
See this page to explore three arguments:
Paul's aiming to know Jesus-biography shows that Paul did know Jesus biography because witness-based Jesus biography was pervasive, especially for Paul; it was hard to avoid and easy to acquire.1
Rather than getting it primarily from other sources, the evidence we have suggests that Paul was overloaded with information on the historical Jesus that he received specifically from the apostolic/Jerusalem church (e.g. from the apostle Peter himself).
See this page to explie these three arguments:
If Paul got lots of Jesus-biography from the Jerusalem church, it would count as evidence for Paul's knowling lots of Jesus biography because the Jerusalem church was quite knowledgeable. It is where the apostles and primary witnesses resided.
2 Corinthians 5:16 — ”from now on we recognize no one according to the flesh; even though we have known Christ according to the flesh, yet now we know Him in this way no longer.”1
No, Paul is simply saying he no longer sees Jesus from a pre-conversion point of view.