I can help answer your questions. It may take some time for me, though, as my schedule currently only permits 1 hour of free time.
500 questions in 20 days means at least 25 questions each day, which I can better handle than 500 questions all in 1 day. The fastest I have done is a 100-question questionnaire, each question consisting of 1 sentence of at most 20 words, in half an hour.