Hadith.1155 - The Prophet صلى الله عليه وعلى آله وسلم was leading his companions in prayer one day when he heard the crying of a child, so he shortened the prayer.
The Imam should recite in a moderate manner because Allah سبحانه وتعالى, the Almighty, says:
"Do not be loud in your prayer, nor too quiet in it" (Surah Al-Isra 17:110).
When the Imam finishes reciting Surah Al-Fatiha, those behind him should say: "All praise is due to Allah سبحانه وتعالى, the Lord عز وجل of all worlds."
It is not permissible to say "Ameen" after the recitation of Surah Al-Fatiha because that was the practice of the Christians.