What kind of foreign trade job do you want to do? Customs declarers mainly handle customs clearance procedures such as customs declaration and tax payment for import and export goods.

The inspectors mainly apply for inspection at the Entry-Exit Inspection and Quarantine Bureau. Exporters are mainly engaged in import and export trade (to put it bluntly, salesmen). Documentary letter of credit is mainly used for foreign trade settlement business. The buyer and the seller shall handle the transportation, insurance, commodity inspection and foreign exchange settlement of goods with the documents applied for in the import and export business. The merchandiser tracks the operation direction of products and services according to customers' orders.

If you are studying English, my suggestion is to export, which is more developed. However, if you are an exporter, you'd better read the documents, which will be of great help to your foreign trade.