This begins a new section of the letter. Here the word "if" does not mean Paul doubts or is unsure. He is emphasizing that these statement are true. AT: "Now you think of yourself as member of the Jewish people"
If your language has a way to mark that 2:19-20 interrupts Paul's main argument of [Romans 2:17](./17.md), and [Romans 2:21](./21.md), use it here. You might have to place 2:19-20 before 2:17.
Both of these phrases mean basically the same thing. Paul compares a Jewish person teaching someone about the Law to helping a person that cannot see. AT: "that you yourself are like a guide to someone who is blind, and you are like a light to someone lost in the dark" (See: [[rc://en/ta/man/translate/figs-parallelism]] and [[rc://en/ta/man/translate/figs-metaphor]])
Here Paul compares those who do not know anything about the Law to babies. AT: "and you teach those who do not know the Law" (See:[[rc://en/ta/man/translate/figs-metaphor]])