Is there any source where the sounds of the letters can be heard pronounced such as in the first year of a high school language?. ą sounded like the french on to me but slightly less nasal but I saw it should be like om.
Ę ≈ French In, En (Singe, serpent) ≈ English Eng (English (without pronunciating the G); Ą ≈ French On (Avon) ≈ English Ong (song)
From what I see, the second vowel in "serpent" is a schwa, so it's basically a very vague sound.
Does this mean "thank you but i decline" or "no, you don't thank me, i thank you"?
For the second one you could say "Nie, to ja dziękuję!", especially with stronger intonation on "ja".
It's just like in English: –Czy chcesz herbatę? (Do you want tea?) –Nie, dziękuję. (No, thanks.)