"Do you remember this horse?"

Translation: Pamiętacie tego konia?

[polec2]

Why can't I use ''Pamiętasz ta konia"?

[Jellei]

Because it wouldn't make any grammatical sense. Koń is masculine, so it's "ten koń" and here "tego konia" because "pamiętać" takes accusative, and even if the noun was feminine, the accusative would be "tę", like "Pamiętasz tę regułę?" - "Do you remember this rule?"

Watch out: maaaaaany Polish people would incorrectly use "tą" in the sentence I just gave, especially in speech. It is incorrect though, the accusative form of "ta" pronoun has to be "tę".

[polec2]

Thank you :) Makes more sense now, I saw an ''a'' at the end of ''konia'' so I said to myself that it has to be feminine. I should pay more attention to the cases.

[Lija611373]

Explain me again please.. why its incorrect pamiętasz tego koń?
(I only have the phone app so maybe missing work structure lessons/notes)

[alik1989]

You need the accusative case here. With all masculine animate nouns the accusative looks exactly like the genitive.

https://en.wiktionary.org/wiki/ko%C5%84#Declension_2