The dialect and the pronunciation of the reader of questions
Could someone tell me which dialect of Arabic is used here by Duolingo? The reason I'm asking is because pronunciations of: 1- "AYN" (coded by "3"), rarely sound like what we normally hear when we listen to Koran here in Turkey. The reader pronounces this sound differently. Examples: (a) "bii3" as "biiyya", (b) "ki3aa" as "kighaa" (softer than Scotch 'ch'), (c) "3ab" as "ab" (like German 'ab') (d) "3us" as "us" in Italian "usare",.. etc. The closest sound I could describe for "ayn" is a bit stronger form of uttering the "Eİ" sound in German "EİN".
2- "C", instead of soft "c", like the English "j" in "judge", "Judy" etc., always sound like French "J" as in "jour".
I didn't do the Arabic courses here myself since I'm a native speaker, but seems you are mixed up a bit between (ع) [Ayn] and (غ) [Ghayn] and (ء) [Hamza]. For the first two letters, maybe the dot above the letter is confusing (many people here complain about the font size and letters do not show properly). As for the (ج), there are some variants: Egyptians say it as "G" and people of the Levant (Şam) say it as French "J" - but the proper way to say it is exactly how the Quran is read and was revealed with, and this sound is exactly like the Turkish "C". Some people say other variants are OK or normal, but honestly, not to me. We always learn this sound in school as "J" in Jacket in English or as "C" as in Turkish. Not soft, and not "G".