I am an Asylum seeker in Italy and I plan to get married to my German fiancée here in Italy soon. Is it possible for us to move to Germany after our marriage with our Marriage Certificate and my Nigerian passport?
Since your financee is German, doing so falls under German rather than EU rules if your fiancee is normally living in Germany. You must apply for family reunification which should be granted unless the authorities think it is a sham marriage.
For details on that, ask on Expatriates Stack Exchange.