1. If you are talking about the Alif in الـ (or the definite article that is), this Alif is always hamzat wassl (ironically, despite its name, there is no Hamza ء above this Alif). Hamzatul Wassl acts a bit like a schwa and its sound is connected to what is preceding it (almost vanishing completely).
2. The Shaddah on ل is natural. Actually, in my answer I didn't use any diacritics (this is how we usually write and type in daily life, i was Just explaining the sequence of letters). Probably Duolingo did not explain this concept yet, but in Arabic and by the nature of letters, there 14 letters that are dubbed as "Lunar letters" and another 14 dubbed as "Solar" letters". Not to go deep, it is a phonetic necessity. The solar letters (which including L ل) are letters that require the merge of the (L) in (AL) into the first letter of the word and forming double letter (Shaddah). Example: شمس (šams) -> الشّمس (aš-šams) [sun -> the sun]. Notice that I'm typing the pronunciation here in my transliteration and not a letter-to-letter depiction. Experiment with your tongue, and try to ALSHAMS, I'm sure you can say it, but with certain difficulty, this is because the distance that the tongue has to travel inside the mouth to change positions from saying "L" to "SH" is relatively long. Thus, it naturally comes to us that the position is kept at "SH" and doubled or stressed as ASH-SHAMS. This is what we have here with اللّيل by nature since the letter itself here is doubled in fact: AL-LAYL -> ALLAYL.
Bonus: Maltese in fact uses the same system but since it is written in Latin, they do change the spelling of the definite article, unlike in Arabic where the spelling of the word and the definite article is not changed. Example in Maltese:
qamar (moon) -> il-qamar (the moon).
xemx (sun) -> ix-xemx (the sun).
check it out with Google Translate.
Depends on from what side you see it. For an Arab like me, I see it like a dialect with Italian, English and French influence, just a bit more than the Maghrib region dialects a bit. But maybe in an academic linguistic sense, it is a separate language naturally. Moreover, you have the "self identity" and some geo-political issues that would emphasize the nature of the language, to be some official language for a sovereign independent state.
Anyway, for me as an Arab, I've been in Malta for a short vacation in 2015 and I almost understood the written word all the time, in hearing I couldn't focus much (but mainly i have my own weaknesses in hearing so I'm not to scale this).
Thanks for this, TJ_Q8. But there seems to be a bit of a paradox. Given that the L of the article assimilates to the first letter of the following noun if it's a sun letter, there doesn't seem to be much meaning in saying that the L of the article assimilates to the L of the following word! How can something assimilate to itself? Incidentally, Duolingo does give us the list of sun and moon letters in this chapter (Hobbies).
I'm not sure I understand that completely. Anyway what my answer was about is that the definite article in Arabic changes its pronunciation but does not change in writing. For solar letters specifically, the sound of (L) of (AL) is dropped and instead the first sound of the noun is doubled (with Shaddah); e.g. šams (sun) becomes aš-šams (the sun), instead of al-šams
We've lost our REPLY function! So I've borrowed it from my previous contribution. No, I understood about the assimilation of the L of the article, like in the example you give - šams (sun) becomes aš-šams (the sun), instead of al-šams. You made that very clear. My point was that it doesn't make sense to say that the L of the article becomes the first letter (if it's a sun letter) of the next word if that sun letter is L. L can't become L, it already is L.