Race - According to World Atlas, the " Race" is to describe the physical characteristics of a person, such as skin color eye color and facial structure and hair color.
Ethnicity - Ethnicity on the other hand is to describe the cultural identity of a person, such as language, religion, nationality, ancestry, dress, gesture, and customs.
According to World Atlas, " Shanghai ranks first in the list of most populated cities in China with a population of 34.0 million people. It is also the biggest city in the world by population"