will companyies be closed during the mid autumn festival

It depends. Some companies may be closed, others may be still in operation.

Dear Belen,

you need to check with directly with the company. In my experience companies will work at least with a skeleton crew over holidays provided there is enough pressure from their customers to finish their many times long overdue projects.
Companies often promise to work through holidays with a full complement of workers, but this is usually not the case.
This information is based on 12 years work experience in China and is true for large state owned and privately owned companies in the field of welded steel structures and machine building.

I hope this information is of any use to you and good luck to you in China.

Robert