Change Visa type

I'm a Ghanaian who is currently living in Wuhan, China. I entered China with a student X type and now, I have been able to get a job here in Wuhan.
It's no doubt that I need to get back to Ghana to switch from an X2 type to a Z-type. At the moment, I have been able to get the documents to help me process my application in Ghana.
I am planning on returning to Ghana in this week then I do the application for the Z-type processing.
My question or concern is that, do I need to provide any other documents aside the ones provided by the company here in China?
And how long does it take to process the work Z type? The company needs me to do the application as soon as possible so I can start working in China.
Please if there are any additional documents I need to provide, kindly inform me so I get them ready.
Thanks and I'm waiting for your honest reply.