What is the ruling on putting forward someone who does not master Al-Fatihah to lead the prayer, and what is the ruling on repeating the congregational prayer individually after doubting the imamate of a non-Arab?

What the questioner did by repeating the prayer is correct and obligatory, because it is not permissible to pray behind someone who makes a mistake that changes the meaning in the Fatiha. This imam's prayer is not valid unless he is unable to learn, but it is not permissible to pray behind him, except for someone who is like him in his inability to recite the Fatiha without error.