Besides, sir is sir, sir, officer. Show respect
Mr. Li and Mr. Zhang are Mr. Li and Mr. Zhang, or Mr. Li Changguan and Mr. Zhang, or police officers Li and Zhang.
PS: Before the British colonial rule in Hong Kong, it was a speaking habit to have English words in Chinese. Therefore, in general Hong Kong films, there are many surnames+Mr..
It's not maden, it's madam, which means lady, lady, madam.
Show respect.
Example: Mrs. Li, Li Furen and Mrs. Li. . .