Paul is describing a situation that does not exist to emphasize that people are persecuting him because he is not preaching that people need to become Jews. This can be stated in active form. Alternate translation: "Brothers, you can see that I am not still proclaiming circumcision because the Jews are persecuting me." (See: [[rc://en/ta/man/translate/figs-rquestion]] and [[rc://en/ta/man/translate/figs-hypo]])
Paul is describing a situation that does not exist to emphasize that people persecute him because he is preaching that God forgives people because of Jesus' work on the cross. (See: [[rc://en/ta/man/translate/figs-hypo]])
This can be stated in active form. Alternate translation: "the cross would no longer cause people to stumble" (See: [[rc://en/ta/man/translate/figs-activepassive]])
Here the words "stumbling block" are a metaphor for something that angers or offends some people and leads them to reject the truth. In this case the "stumbling block of the cross" is the teaching that people are saved by "the cross" and not by the obeying the law. People who choose to believe that salvation comes by obeying the law are offended by this teaching. They "stumble" when they reject the teaching about the cross. Alternate translation: "the offensive teaching about the cross" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here "the cross" is a metonym for the teaching that because Jesus died on the cross and is alive again, people are saved by believing in him. Alternate translation: "the message about the cross" (See: [[rc://en/ta/man/translate/figs-metonymy]])