Volunteering

Since I will visit Germany in order to attend Frankfurt Book Fair from October 14h to 18th, I have been looking for a volunteering position.
So I could stay there during two or three more weeks. I would like to have some accommodation in exchange of my voluntarh work.
Last month I was in Northern Ireland joining in some Conservation Volunteers Northern Ireland (CVNI), and I wish I could go and visit Germany. That is why I am looking forward for your help. I am Brazilian writer, 37
(male). You can contact me at [Email caché]