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.
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