What could be sold to Chineese in empty containers when they travel back to China ?

From where? Every place, country, has its own preferred goods. The most important thing to remember is that production costs in China are very low hence whatever you want to send to China must have been produced cheaply too in your country in order to be able to compete with chinese production. Nowadays, there is almost every thing in china, produced locally and cheaply.

So, my first question is FROM WHERE?

All the best!/