Actually, if people say Chinese is a language, it is not entirely wrong.
Mandarin is the official language in China. Cantonese spoken mainly in Canton region is one of the many Chinese dialects among others; all those languages are called Chinese. The grammar is the same. Every Chinese-speaking people understands Mandarin, but not all understand Cantonese.
Chinese characters used in mainland China is simplified. Simplified Chinese characters were introduced in mainland China mainly to reduce illiteracy since 1950s.
Good question. In English, we have to use “how” after “know” in a sentence like this. I know it’s not used in Spanish or Portuguese, so it’s confusing, but “how” is necessary here. For English speakers, our challenge is to remember not to include “how” when we’re translating to another language.