"he seriously told them and begged them." Here the words "testified" and "urged" share similar meanings and emphasize that Peter urged them strongly to respond to what he was saying. Alternate translation: "he strongly urged them" (See: [[rc://en/ta/man/translate/figs-doublet]])
The implication is that God will punish "this wicked generation." Alternate translation: "Be saved from the punishment that these wicked people will suffer" (See: [[rc://en/ta/man/translate/figs-explicit]])
Possible meanings are 1) Peter was urging people to let God save them. Alternate translation: "Let God save you," or 2) Peter was simply urging them in a general way to avoid being punished. Alternate translation: "Save yourselves" or "Flee" or "Escape" (See: rc://en/ta/man/translate/figs-activepassive)