3 months in Berlin?

Ok, so there is couchsurfing.com for short stays, a wonderful site with great people all over the world.  There is also houssitting.com, also a good site,  but "offers" to stay are few and far between (and none  so far in Germany:  tons in the US, a few here and there in Europe, e.g. France, Italy, Belgium..)  I would love to be able to come to Germany and be able stay for about 3 months and get to speak German. I can read and comprehend German. I can speak and understand "tourist stuff" so what I seek is either a sort of housesitting  or perhaps a kind soul who will give me free lodging for about 3 months, possibly in exchange for either English sprache oder Französisch spache.