In Duisburg, Essen, and Mühlheim the Studierendenwerk Duisburg-Essen offers student accomodation. Here you find the Studierendenwerk’s overview page on accomodation.
Register directly for accomodation on this page: Student service (language switch on the right top of the website)
Join ‘Start with a buddy’s facebook group and post that you are looking for accomodation: Buddy group (for every student at Folkwang)
Portals for the private housing market are immobilienscout24.de, immowelt.de, kalaydo.de, meinestadt.de, wg-gesucht.de, and wohnungsboerse.net.