"He is a good boy."
Translation:Ele é um bom menino.
I don't understand why you can't use "boa" instead of "bom". Are they not interchangeable?
no. most adjectives have feminine and masculine forms. Bom garoto (good boy - masculine), boa garota (good girl - feminine)
"Guri" is a Brazilian regionalism for "menino"; i.e. it means "boy", not "good" (bom). I'm not sure what mistake you made (if any), but that surely wasn't it.
Good luck with your studies :)
The order is interchangable. However its more usual with bom before. Regardin "homem" that is wrong because wthat is man and not boy.
Let me first correct you terminology so as not confuse others. The issue is adjectives that come before nouns. There may be cases I am not thinking of, but for the most part adjectives don't modify pronouns.
In Spanish, the majority of adjectives come after the noun. Certain adjectives like those that quantify always come before the noun. But there are a group of adjectives known as meaning changing adjectives, that change their meaning somewhat depending on whether they go before or after the noun. Bueno/a is actually considered to be one of them, but the meaning change is not really meaningful in English. Essentially adjectives are considered more subjective if they go before the noun and more objective afterwards. Since what is generally somewhat subjective, bueno/a is quite often found before the noun.
Here is a link that reviews the placement of adjectives in Spanish
Oops, you are discussing Spanish on a Portuguese lesson page. I have done that before. "bom" and "boa" are being discussed here. https://www.duolingo.com/skill/pt/Adjectives-I/tips-and-notes This link doesn't go directly there so click on the "Adjectives I " lesson and then click on the lightbulb for the tips and notes.