"Good people send them food."
Translation:Dobrzy ludzie wysyłają im jedzenie.
In plural nouns and also adjectives which describe them are splited into two categories masculine-personal (masculine nouns which name people) and non-masculine-personal (feminine, neuter and masculine nouns which don't name people - things and animals) "Człowiek" (singular) is masculine and this noun names a person so in plural ("ludzie") it is masculine-personal. Moreover it is used in Nominative.
So the adjective "dobry" has to agree with a masculine-personal noun used in Nominative case. Therefore you have to know the pattern in which adjective "dobry" is declinated. Click on the link, go to the table of declension and then check: liczba mnoga -> m.-os. -> Mianownik: https://pl.wiktionary.org/wiki/dobry
Click on the text "declination of człowiek": https://en.wiktionary.org/wiki/cz%C5%82owiek
"dobry" and "dobre" are declinated forms of "dobry"
"dobrze" is an adverb which means "well"