"Our cat eats fish."
Translation:Nosso gato come peixe.
Your example should be correct, I believe, so it's good you reported it. One quick note, though: it only matters that the cat is feminine; whether we are or not, the gender of the possessive adjective (nosso/nossa) is determined by the thing possessed.
So you can say nosso gato or nossa gata
But you cannot say "nossa gato" or "nosso gata", because the gender of "us" doesn't matter here, only the gender of the cat.
the conjugation table only lists Nós, not Nosso :-)
Is there any trick to make a longer re-phrase of the sentence "Nosso gato come" to know that the correct verb is "come"?
Or is it because gato = cat = it?
Er/Sie/es = He/she/it = Ele/Ela/ https://www.duolingo.com/skill/pt/Basics-2