It doesn't sound like in Portuguese. In Portuguese, we don't pronounce the M or N in the end of a syllable, we tend to nasalize the preceding vowel instead. In Ukranian, we do pronounce the N in the end of syllable. And in this case, the N is palatalized, which means that along with the tip of your tongue making the N sound, the middle of the tongue touches the roof of your mouth (hard palate).
adverb is добре (well). You use it just like you would use "well".
Adjective "добрий (добра, добре)" actually mostly mean "kind, nice" or even "tasty", it's less common to use it in the meaning "good". To say "good" there's another adj: хороший (comparative: кращий, ліпший, superlative: найкращий, найліпший)
Addition to Vinnfred's comment: добрий means "good" as opposed to "evil" --> kind, nice; хороший means "good" as opposed to "bad", "bad quality", "nasty". So, "Ти дуже добрий" means "You are very kind" (maybe, to me etc.), "Ти дуже хороший" = "You are very good" (not to somebody but just you're nice)
There's also informal "класний" :) "Ти класний!", "Класне кіно!", "Класний кіт", ....
Mmm, what is крутий then?.. I thought of it too, decided that класний is somewhere between "good" and "cool", cause it's more informal than "good" but still said by parents or about cute and nice things that are not really "coool" :)
But yeah, you're right. It's not a synonym at all, much stronger, you can't say like "Класного ранку" or so xD