It would be helpful for these to be presented a bit more before asking us to reproduce them from recordings.
Is the reason why we don't use genitive because of the use of "to" ?
Is which case, is this correct ? : Wtorek nie jest mojego dnia
No, it's not Genitive, it's Instrumental: "Wtorek nie jest moim dniem".
Tuesday ain't my day should be accepted. Shouldn't it?
Well, you know, "ain't" isn't exactly standard language. It's too colloquial.
Why i cannot reply on someone else's comment?
You have to achieve a certain minimum level to be able to post anything in the Duolingo fora.
Nie obchodzi mnie chy poniedziałek jest niebieskim
Wtorek szarym i środa też
Czwartku, nie dbam o tobie
Jest piątek, ja jestem zakochany