Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear brother in Islam, thanks a lot for your question which reflects your care to have a clear view of the teachings of Islam. Allah commands Muslims to refer to people of knowledge to get themselves well-acquainted with the teachings of Islam as well as all aspects of life.
First of all, it should be clear that after reading the Glorious Qur’an, there is no act of worship better than dhikr and du`a’. The merits of dhikr are highlighted in the following Qur’anic verses:
“Then do you remember Me; I will remember you. Be grateful to Me, and reject not Faith.” (Al-Baqarah 2:152)
“… and for men and women who engage much in Allah’s praise, for them has Allah prepared forgiveness and great reward.” (Al-Ahzab 33:35)
Also, the Prophet (peace and blessings be upon him) said,
“Surely, Allah, Glorified and Exalted be He, says, ‘I will be with My servant as long as he makes mention of Me and moves his lips in making mention of Me.’”(Al-Bukhari)
“No people assemble to remember Allah but angels surround them, mercy covers them, sakinah (calmness) descends upon them, and Allah mentions them in His assembly.” (Muslim)
As for the question of making dhikr in a group, the Fatwa of the European Council for Fatwa and Research, states:
Making dhikr in a group is allowed as long as the following conditions are met:
1- The dhikr is free from munkar or acts that violate the decorum of a Muslim, such as shouting and the singing of love songs.
2- The dhikr must not be done except with the known words mentioned in the Shari`ah, and not unintelligible words or sounds.
May Allah guide us to the straight path and direct us to that which pleases Him, amen.
Allah Almighty knows best.