Iranians spoke Persian and managed to keep their language after the Arab conquest, but Egypt couldn't keep Coptic expect for some small Christian communities. What other languages where spoken where Arabic is now spoken? What was spoken in Irak, Syria, Lebanon...etc?
Not to discourage any further answers, but you might find these older threads to be helpful:
On the history of language in Egypt and the gradual transition to Greek and Arabic by /u/frogbrooks and myself
On the decline of Romance languages in North Africa by /u/Libertat