You is singular in the Greek text. Here, you refers to a hypothetical Jew who feels superior to Gentiles and believes that he is not in danger of judgment. Paul uses a popular Hellenistic writing style called a diatribe (a teaching method that presents a debate with an imagined opponent). In this style, the writer argues against a made-up person in order to persuade the audience.
the same things: Paul’s means that Jews, like Gentiles, turn away from God’s revelation and choose to follow their own path.