Is there any opportunity for a native Italian speaker, half Argentinian, who speaks fluently Spanish and English?

If you’re talking about opportunities for jobs in China - certainly yes! You’ll sadly make less than a native speaker, but they are desperate for english teachers in training centers and schools. I live in Shanghai and work at a training center where most of the foreign teachers speak english as a second or third language.

Generally speaking, English language teachers in China need to be from native English speaking countries, while teachers of a different subject like Math or Science can be from non-native countries. That said, there are always exceptions but if you want to teach English, I would suggest to apply to schools directly.