Translation:I come from China.
Every Kanji has two pronunciations (some very common ones even more). One etymologically from original Japanese, the other from Chinese. Both are used just as much. A rule of thumb is that when they are used on their own, they often are pronounced the Japanese way and when in combination with another kanji to form a new word, they are pronounced the Chinese way. Ex: お国は何てすか？ 中国です。 Is pronounced "Okuni wa nan desu ka? Chugoku desu" and translates to "What's your country? It's China" (or more smoothly, "What country are you from? China") Similarly, 中です would be pronounced "naka desu" and mean "it's inside" So 中 = Naka (Japanese) or Chu (from Chinese Zhong) = inside/middle 国 = Kuni (Japanese) or Goku (from Chinese Guo) = country. So you'll have to learn both pronunciations for every word as well as when to use which.
It's both. The main thing about the kanji is not the sound, but the idea and meaning (atleast that's how I understand it), and thus one symbol can have different sounds, or readings, but carry the idea of country or domain. Just like English also has different words or sounds for roughly the same idea, but in English we write the sounds of the word, and not the meanings and ideas behind it with different symbols.
We don't, we need to rely on context. I doubt duo has entered I/you/he/she/it/they for every answer, so i would answer with the assumption you are talking about yourself. We could go further and say the dog is from China, the cat is from china, the panda is from China depending on what the conversation was talking about before this sentence.
Alot of japaneas dont state pronouns unless they really wanna speficy it but everything is implied XD so in a sentence where it doesnt state a pronoun like "america shushin desu" it can literally mean, i/ he/ and or she is from america, just matters on the context but mainly if ur gonna start a convo or something where theres no context before the sentence u said with no pronoun, itll of course refer to yourself but lets say ur talking about a dif person, and u just wanna bring up shes from america, thats when u would be saying "amerika shushin desu" or "amerika jin desu" and means SHE is/from america, not I but basically it means all pronouns but its kinda confusing for beginning learners, like id still consider myself a beginner but atleast ik some stuff and how to contrust basic sentences