What should I do if I finish reciting Surat Al-Fatiha in congregational prayer before the Imam in the rak'ahs where Al-Fatiha is recited? Should I recite Al-Fatiha again or supplicate as I wish?

The worshiper should not remain silent if he finishes reciting before the Imam in a silent prayer. Nor is it prescribed for him to repeat Al-Fatiha. Rather, he should busy himself with reciting more of the Quran or making supplication.