If you are speaking with any sort of authorities, police, doctors,
etc. its best if you speak your native language.

In China, most authorities don't like it when someone argues with them, especially in their own language. I've seen it happen, it doesn't end well.

Always remember that, actions speak louder than words, language is just a tool to get others to do what we want, and certain words can also be perceived as a weapon, so choose your words carefully.