With the order you suggested, it means that the professor is originally Canadian, and currently an Arab, while the original sentence is the reverse (originally Arab, and currently Canadian) - the most current status in English comes before the noun right away. In Arabic, the current status comes right after the noun.
I have an Arabic/English dictionary that I like to check when these questions come up. It translates استذ as professor and مدرس (mudarris) as teacher. Since a professor is someone with a doctorate who teaches at a college or university and the term "teacher" is used for someone who teaches at a school for lower level students, I assume that the same is true for the Arabic.
Could be a technical issue, since the audio generally is produced by a machine and not a real person.
This said, the ending of words in the middle of the sentence is supposed to change according to its grammatical status and not as the audio here says it (and in this case "Canadian" should be "kanadiyyun" but Duolingo machine is not spelling it that way).