Are you suppose to just listen the hamd of the Imam? What if you are too far away? Where should your mind be set to? Can you say any dhikr if you can't hear? If so what dhikrs are recommended?
You listen. And you remain silent even if you can not properly hear.
So, when the Quran is recited, listen to it, and be silent that you may receive mercy.
During jama'at if you're not hearing what imam reading just keep in your mind Allah is seeing you. Your eye focus should be on your foot. We'll not get any bad thoughts if we keep in mind just one thing "Allah is seeing me." May Allah peace upon us.
In all cases, you're obligated to recite Surah Al-Fatiha in Salah. If it was a Salah (fajr, jumuah, first 2 rakahs of maghrib, first 2 rakahs of Isha) where an imam recites loudly, then also recite Al-Fatiha, but don't recite a Surah after it.
Abu Huraira reported:
The Apostle of Allah (ﷺ) said: If anyone observes prayer in which he does not recite Umm al-Qur'an, It is deficient [he said this three times] and not complete. It was said to Abu Huraira: At times we are behind the Imam. He said: Recite it inwardly, for he had heard the Messenger of Allah (ﷺ) declare that Allah the Exalted had said: I have divided the prayer into two halves between Me and My servant, and My servant will receive what he asks. When the servant says: Praise be to Allah, the Lord of the universe, Allah the Most High says: My servant has praised Me. And when he (the servant) says: The Most Compassionate, the Merciful, Allah the Most High says: My servant has lauded Me. And when he (the servant) says: Master of the Day of judg- ment, He remarks: My servant has glorified Me. and sometimes He would say: My servant entrusted (his affairs) to Me. And when he (the worshipper) says: Thee do we worship and of Thee do we ask help, He (Allah) says: This is between Me and My servant, and My servant will receive what he asks for. Then, when he (the worshipper) says: Guide us to the straight path, the path of those to whom Thou hast been Gracious not of those who have incurred Thy displeasure, nor of those who have gone astray, He (Allah) says: This is for My servant, and My servant will receive what he asks for. Sufyan said: 'Ala b. 'Abd al-Rahman b. Ya'qub narrated it to me when I went to him and he was confined to his home on account of illness, and I asked him about it.
While you are behind Imaam, during Jama'at, distance from you to Imaam makes no difference, you make a promise (niyat) I am performing my Salah behind this Imaam, my directions towards qaabaah (qibla)(mecca) Allah hu akhbar...
It is prohibited to go ahead of Imaam and so it is against to recite what Imaam is reciting, we just have to listen what Imaam is saying or reciting no matter the namaz time is fajr, zuhar, asr, magrib, isha when you are behind Imaam you must be quiet, Imaam prays on behalf of you and if Imaam says wrong or does mistake you must give him suggestion (luqma in Urdu we say) in namaz for correcting Imaam so that if Imaam prays' perfect our salah will be perfect
If also Imaam don't recite aloud as in case of zuhar and asr be quiet,
cases where we need to read:
1)Takhbeer e Tehrima - saying Allahu akhbar behind Imaam at the start of salah.
2)Tasbeeh when we bend down ruqu (an act of bowing down like perpendicular L shape after surah is done).
3)When we stand after ruqu Imaam says
Sami allah huliman Hameeda
we must reply softly,
Rabbana wa lakal hamd and
4)Tasbeeh for sajdah (when we lay down with our forehead touching the ground)
5)When we sit we must recite. tashahhud, darood e ibrahimi and surah ma'oon.
6)As salam mu alaikum wa rah matullah on both your shoulders on finishing salah.
that much only.
and if you are performing salah alone you must read it all.
May Allah Make your Salah perfect so that your dua gets accepted