Translation:Our ice cream will be made from milk and fruit.
Oh, my; I didn't know they were declined differently. Thank you! Can you help me with another example, please? Is this correct: z Polski = from Poland = with Poland?
z Polski – from Poland
z Polską – with Poland
You use genitive to mark the origin, and instrumental to mark companions.
Such things as hyphens aren't marked, so either something else was wrong, or there was a bug...
Has it been explained anywhere when to use 'być' and when to use 'zostać' for the passive and if there is a difference?
Well, they literally translate to will be/will become, but then in English 'will become' is a lot less probable than in Polish... I guess that 'zostaną zrobione' focuses on the moment of them being made more? In such a sentence as this one, I think they mean the same.