Here "city"refers to the people in the city. Alternate translation: "most of the people of the city were divided" or "most of the people of the city did not agree with each other" (See: [[rc://en/ta/man/translate/figs-metonymy]])
The second group mentioned agreed with the message about grace. It may be helpful to restate the verb. Alternate translation: "sided with the apostles" (See: [[rc://en/ta/man/translate/figs-ellipsis]])