Conjugation of verb "lire" : je lis, tu lis, il/elle/on lit, nous lisons, vous lisez, ils lisent.
When the sentence is played, she says li(s), but when "lis" is pointed out to be said alone, she pronounces the 's'. I'm pretty sure, with my limited knowledge, you don't pronounce the 's', but is there any reason it is pronounced when said alone on duolingo?
you are right, "lis" or "lit" are pronounced LI.
however, although it is optional, you may hear a Z liaison in some cases: je lis un livre = je LI-Zun livre.
I always had this question: why the verbs can be translated to the present form and the present continuous form simultaneously?
There is no continuous tense in French, that is why. When you want to translate an action in progress, you can use a phrase: "être en train de + infinitive": "Je suis en train de lire le menu".