"Potrzebuję dużej butelki."

Translation: I need a big bottle.

[katracsal]

Is this genetive? Does "potrzebuję" take the genitive?

[immery]

yes. it is genitive, yes potrzebuję needs object in genitive.

[rfl.kt]

Why not "I require a big bottle"?

[Jellei]

I think it really translates to "wymagam" and sounds rather strange.

[freekarol]

Why is it not dużej=bigger?

[katracsal]

The -ej ending is because it is genetive.
I need a bigger bottle = Potrzebuję większej butelki (I think!)
Duży/dużej= big
większy/większej=bigger

[freekarol]

Thanks, it's clear now. I must find something good about Polish grammar because learning words is easy but I still don't know rules of conjugations and declensions.

[Glen624972]

Z powodu wirusa Corona muszę zostać w domu. Potrzebuję kilku dużych butelek.