"I do not remember if he had cleaned the apartment today."

Translation: Nie pamiętam czy sprzątał dziś mieszkanie.

[EvelinaEliana]

"dziś mieszkanie" vs. "mieszkanie dzisiaj" - Is my answer (the second one) wrong? It didn't accept it. Are they interchangeable? Is it a case of one being more comment or perhaps a dialect difference?

[luless]

Both are correct, but first one is more natural - second needs some more context to sound natural i.e.:
'sprzątał mieszkanie dzisiaj czy wczoraj'