porquê (adverb why) = answer in the end of when you refer to the reason
Notice that porquê is also a masculine noun, "reason, cause"
Tip: When used in question, write por que/quê apart and when answering, write together. Write que with an accent when it is used in the end of sentence. Notice however the different meanings of the words.
Asking politely
em português   in English Poderia me dizer ……?   Could you tell me ……?
poderia   to be able to , can Look irregular verbs poder dizer   to say irregular verbs dizer