This happens because many products made by China, came here with cheaper prices, being very competitive compared with national products even products from other countries. I heard that government already put large taxes in some products to protect the national companies.

I know what it means but I don't understand why China? Why not America or Russia or some other country?

Hi Mia. I'm from Brazil. That expression "um negócio da China " mean a great business with great economics advantages.