To be a Jew can mean to be an ethnic descendant of the Tribe of Judah or of the Kingdom of Judah (which comprised portions of Benjamin, Levi and Judah - even some Simeon),
To be a member of the religion of Judaism.
When I speak of Jews, I'm referring to the first definition - not strictly members of the religion of Judaism that has every race in its ranks. I've spoken out against those "Jews" pretending to be ethnic Joes, etc.
Michael's Freund's fraud: Indian converts pretending to be Joes!
Paul was a Jew by his association with those of the former Kingdom of Judah, and by their religion. He still claimed to be, present tense, a Pharisee - but with a new and improved understanding. Yeshua and the early Church of God, those ethnic Jews and Israelites in it, were also Pharisees.