"We do not know that girl."
Translation:Nie znamy tamtej dziewczynki.
Nie znamy tego psa(dog)/krokodyla(crocodile)/chłopca(boy)/zwierzęcia(animal) - so I guess it doesn't matter here. :)
When you negotiate a sentence, accusative turns into genitive. E/3 (F) in genitive is jej so other pronouns also add the same suffix, so it turns out to be tamtej the correct one.
Why do you think it's tamtego when it's right I went ask my dad if it's right and he said it's right and he is polish
Yes, it is genitive. Feminine nouns in genitive end in either -y or -i.
'Dziewczynką' is instrumental.
Dziewczyna is a correct translation , but you need genitve after "nie znamy"
Nie znamy tamtej dziewczyny.
It's a very common rule in Polish. If a positive sentence needs Accusative (My znamy tę dziewczynkę), then when negated, it switches to Genitive (My nie znamy tej dziewczynki).