How did Yu Qiaqing know about the business of Lulin Foreign Firm?

Lulin foreign firm not only imports pigments, but also deals in western medicine, hardware and military uniforms, and exports cheap agricultural and sideline products such as soybeans, tung oil, silk and tea. For these import and export businesses, Yu Qiaqing was very familiar with them, and he was good at selling them, and the business also improved, so he was soon promoted to comprador when he entered the foreign firm.