Why is it not Soy de China. Because soy means I am so it would still be I am from China right
Okay. Now " Soy de China" is the same as " Yo soy de China" Sometimes "Yo soy" is frequently used than " Soy "
To show that you are from it. "de" is a possessive particle so when you use it in sentences it can show that someone owns it.
No, they would learn on Duolingo that they should say Yo soy de China when they fly to exotic Mexico for their vacation