Mr.francois, the company should apply for the following two documents for you: Employment License for Foreigners issued by Ministry of Human Resources and Social Security of China and Original Visa Notice Form issued by authorized departments of Chinese Government

if you have the two documnets, you can prepare your original passport, one completed visa application form affixed with one recent passport photo,

then go to the Local Exit & Enter Department under the Shanghai Public Security Bureau to apply for work visa. if your application is refused, you have to exit Mainland China to apply for work visa, then enter China again, apply for residence permit within 30 days after entry at the local police station.