Maybe all Germans already know reasonably good English.
Nobody in Germany wants to learn Arabic, and everybody already knows English. So there is no market for your offer. Or very little at least. If you want lessons, pay for it. It is not that expensive.
A German (who just wants to drop by) - I think most Germans here, as Chris said have a decent level of English so you need to "lure" them with another language :P
In my case it's Japanese... but well, finding a partner there is the same problem xD
I want to learn German as well- but it can still be really effective to speak the language you're learning with another student. If anyone is learning German and wants to practice speaking, let me know!
Hi! I can understand you problem... If you want to practice German I can help you! I'm not mother tongue, <em>leider</em>, but I had been learning it for a long time and spent some time in Germany to practice it and I would refresh it a little bit so... Contact me if you want!