Got a denial letter for unemployment, what now? (Portland)

I got a denial letter last week saying I left my job voluntarily, but I was let go as a janitorial supervisor. I am in Portland, in case local advice matters. The letter lists a deadline and a hearing process, but it is hard to follow. Did you bring documents or only talk?

Stay calm and stick to facts. Mine lasted about thirty minutes and felt more like a conversation than a trial.

Keep everything in writing and save the confirmation numbers. It saved me later.