Mr.gerard lamas, yes, you need a visa to Guangzhou, China, your supplier needs to send you the below documents to you:
1. An invitation from CHINA with a copy of the business license
2. Visa notification letter from relevant authorities in China, such as Guangzhou Foreign Affairs Office, Guangzhou Bureau of Economy and Commerce.

Then you can apply for a Business Visa to China by provide the below 2 documents and your passport, one passport photo, one visa application form, the Congo residence permit and its copy.