Entry and exit inquiry

Hello! :-)

I am a Nigerian with a multiple entry Mainland L visa. My current stay of 30 days is expiring on the 16th of April. I need to go to Hong Kong and come back into Mainland China shortly. How long will it take to process this type of visa? Is there still time? I was told it takes six weeks to process the visa but I don't want a long visa, I just need one or two days to get into Hong Kong and then come back into Mainland China again. I would be exceedingly grateful to hear your input on my inquiry. I need to figure this out immediately!!!

Thanks and have a lovely week!