The William Booth House is a facility of housing for the homeless and or mentally ill people of Berlin, offering suppor tailor-made around each individual. See how you can help them here. https://www.heilsarmee.de/spenden-bereiche-einrichtungen.html?fb_item_id=10141
Join the facebook page and see how you can help the homeless during their rough times.
https://www.facebook.com/helfenisteinfach/?fref=ts
Accomodating for upto 71 homeless people of the city of Berlin and providing them with emergency shelter, see how you can help them and donate your time/funds
http://berliner-wohnplattform.de/kontakt
Rise Foundation e.V supporting the homeless through their tough times, providing them with food, shelter and other needs that the less fortunate may need to help them get by. Contact them to be involved in their work or donate to the cause.