forgot Apple ID and password

Hi! I have iPhone 5S which I have bought few years ago. I have all documents ,sale receipt and goods confirming that this iPhone is mine. One week ago I have updated my phone to iOS 9.3 and after that iPhone asked for Apple ID and password. Truly I have forgot both. I've tried lots of variants all false. I don't know what to do, I can't use my iPhone for a week. Can u help me?