My Father petition me in 1993 and he died before my Priority Date. I submit to NVC the Death Certificate & after that USCIS sent me an email saying:

On May 12, 2011, a USCIS office received thiscase from the State Department with a request that we review it. We will notify you when we complete our review, or if we need something from you.

For approved applications/petitions, post decision activity may include USCIS sending notification of the approved application/petition to the National Visa Center or the Department of State. For denied applications/petitions, post‐decision activity may include the processing of an appeal and/or motions to reopen or reconsider and revocations.

Can you tell me exactly, what to do? how many months it takes to wait for the decision?