What is the ruling on reciting Al-Fatiha after every obligatory prayer, and is the intention behind audible remembrance after prayer congregational remembrance, and what is the ruling on congregational remembrance?

There is no authentic evidence for the permissibility of reciting Al-Fatihah after the obligatory prayers. However, there is no harm in reciting it occasionally. But to persist in it and consider it a Sunnah or a required remembrance after prayer is an innovation (bid'ah).