Is there a Sunnah prayer for Friday Prayer before or after it?

There is no regular Sunnah prayer for Jumu'ah before it. It is prescribed for a Muslim, upon entering the mosque, to pray as many voluntary (nafl) units as he wishes, in sets of two rak'ahs, without specifying a number of rak'ahs. The minimum for this is two rak'ahs as a greeting to the mosque (Tahiyyat al-Masjid). As for after it, there is a regular Sunnah prayer, the minimum of which is two rak'ahs and the maximum is four.