Accusative. "Bread" is not animate, and for masculine non animate nouns their Accusative is the same as Nominative.
Having said that, there are quite a lot of nouns that are grammatically 'animate' for no reason, including most vegetables and fruits. But you will encounter it later, let's leave that aside now.
in Polish a yes/no question is form by either adding the word "czy" before a statement, or just changing intonation (speaking) /adding "?"( writing). Latter is less formal, but perfectly correct.
(although I think beginners really should create their questions with "czy" as it makes things clearer)