Question Summary:
Should I recite anything behind the Imam?

Question Detail:

Should We Recite Surah Fatiha Behind Imam In Namaz or Should we Remain Silent 
And We Should Follow Imam Then In Zohar Namaz  Imam Recites Silently , So We Should recite our own or imam is Reciting ours 
Same Goes for 3rd Rakat of Maghrib Please Clarify

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
A Muqtadi (person performing Salaah behind the Imam) should remain silent regardless of whether it is a Salaah wherein the Imam recites loudly or softly. He should neither recite Surah Fatihah nor anything else. He should remain absolutely quite. The Qiraa’ah of the Imam is sufficient for the Muqtadi.[1] 
A person should focus his mind towards Allah as Salaah is a means of communicating with Allah.
And Allah Ta’āla Knows Best
Nabeel Valli
Student Darul Iftaa
Lusaka, Zambia
Checked and Approved by,
Ismail Desai.
www.daruliftaa.net