He speaks fluent First Age Sindarin, and he can manage all the relevant dialetcts that it has shifted to over the millenia. He speaks Taliska and Adunaic, and Westron all fluently
(the only Sindarin he doesn't know is Doriathrim, because the Doriath people don't talk to any Noldor who aren't Arafinwean, and then there was Murder so uh yeah)
He probably has a few scattered base phrases in old First Age Khuzdul from the times when they were allied with, and quite possibly even lived with Belegost during the wars
He probably has a bunch of different accents that he picks up and discards over the years depending on what is least likely to get him kicked out and most likely to earn him coin for meals and bed
Turgon speaks Quenya, and High Valinorean Formal Proper Quenya Without That Stupid Lisp at that hilariously, locked away inside Gondolin as they were, he probably sounds really old-fashioned to everyone else
Elladan speaks Third Age Sindarin as his cradle tongue, and Westron as his second. His Quenya is a distant third, and hilariously because dad was partially raised by Feanorians, he flips back and forth about the lisp
Erestor, well, my version of Erestor, speaks Sindarin as his first language, and Feanorian Quenya as his second, except when he's actually in formal situations rather than just speaking quenya informally, in which case he loses the lisp because it would not be politic to use it. He prefers Sindarin though.
Kaito speaks fluent Jap, high-school level English (possibly even a bit better than that, because he seems the sort to learn things that might be useful for funsies), and may have picked up bits and pieces of other languages as he goes
Caranthir speaks Feanorian Quenya, and First Age Sindarin. He has a wee bit more first age Khuzdul than his brothers do, and less than Finrod, Friend to Everyone does. Mostly, he knows numbers /cough
Faramir speaks Westron as his first language, and somewhat bastardised Sindarin as his second. He wants to learn Rohirric the first phrase he learns will undoubtedly be I love you and Quenya
can it be called modern quenya if the shift happened that early in history though i mean come on Fëanorssh let Feanor be a snob it's his mom's namedrama kingwell yeshilariously, locked away inside Gondolin as they were, he probably sounds really old-fashioned to everyone elseTuor taught him all he knows about Sindarin slangthe first phrase he learns will undoubtedly be I love youand QuenyaEowyn will be happy to teach Faramir Rohirric but suggests he finds another tutor as well as their lessons seem likely to get distractedthis is indeed true. also, he wants to surprise her when he tells her he loves her in Rohirric