Polish is the official language (used in the offices) so all applications, forms and other letters for offices should be submitted in Polish.
Nevertheless, clerks should provide information in a comprehensible way and (to possible extent) in the language understood by a petitioner. If it is not possible for you to have a friend who could help in translating, please try to ask for a help of a clerk who knows your mother tongue or other foreign language that you know.
In the Warsaw City Hall (e.g. in citzen affairs departments) there are clerks using sign language
In some cases, the law guarantees you getting information concerning the principles
and mode of conduct and exercise your rights and obligations in a language you understand, e.g. in case of legalizing proceedings (concerning visa issuing or prolongation, permanent residence permit or the EU long-term residence permit) and deportation from Poland.
You can make a reference to the below regulation:
Art. 9 of the administrative proceedings code
Public administration bodies are obliged to appropriately and exhaustively inform parties about actual and legal circumstances that can have influence on determination of their rights and obligations that are subject of an administrative proceedings. That bodies should enable situation when all parties and persons participating in proceedings do not suffer any losses due to ignorance of law by providing all necessary explanations and advices.
