Answers:

steven02345
Sterling

Mandarin is spoken in most of China (especially the North) and it’s the official language of China.
Cantoneese is spoken in southern China (and hong kong). If you go to a cantoneese speaking place chances are they will understand English (more used to foreigners) so Mandarin is a safe bet. Sorry can’t help you with the lessons If I know 5 sentences I know a lot there :) .
good luck with your trip.

nyc326
New York City

Northeast speaks Korean.
People from North also speaks different dialects depend on which ethnic groups they belong to.