[avereveard]

Well ę in część is without the n never heard it with n, but I definitely use the n in words like jęzik, so yeah you cannot generalize between those nasals and "say n if it's in the middle of a word" only goes so far

Ą is a bit more regular at that, so usually loses the n when at the end of a word and never heard without n when in the middle of a word, except in places like Warsaw, and other cities up north, where I was called out as gòralski (which is funny considering I'm Italian, I guess I'm learning polish wrong but convincingly enough)

[hipnoizz]

My first reaction was that I would pronounce 'ę' in both 'część' and 'język' in the same way, i.e. without 'n'. But I can see that pronunciation of these words as per https://en.wiktionary.org/wiki/cz%C4%99%C5%9B%C4%87 and https://en.wiktionary.org/wiki/j%C4%99zyk disagrees. And then a quick search brought these 'simple' four rules (https://sjp.pwn.pl/poradnia/haslo/Wymowa-samoglosek-nosowych...) for pronouncing 'ą' and 'ę' in the middle of a word ;-)

So yeah, everything is easy, simple and obvious when you are a native speaker and I stand corrected :)

[avereveard]

Ah also chcesz I've no idea how to pronounce that maybe an X at the beginning and a fshhhh at the end no idea.