OK I hope we both speak the same language, but as long as we are on moz I do it in english
Otherwise it would be hard for you to optimize that domain...
First, when did you start optimizing? Than, you used a lot of exact match phrases in the content, a bit to much for me when I highlight these words. I think you could link to some pages (like the wiki statistics u cite). You also don't link much intern. You can get a lot of positiv signals by linking intern whenever it fits. You don't have one backlink to that page (not Domain) and thats not normal 
I hope you realized, that the page is perfect for "fernstudium arabisch" (I know taht a lot, lot, lot more people are searching for "larabisch lernen") - you got position one on that phrase. You may should search for some other keywords/querries - because arabisch lernen is possible in a lot of ways - apps, in school, books...
The Text isn't perfectly written, not a lot of synonyms/semantic - seems like you tried to build senteces with the exact phrase "arabisch lernen" - Here is what I mean: "steigenden Bedarf an Menschen, die Arabisch lernen" you know thats not correct - what you mean is "steigenden Bedarf an Menschen, die Arabisch sprechen". You put that phrase in a lot of senteces but excluded the h1 and url. Hmmm..
A lot more things are possible 
Have you looked to the first 10 Results? Some Domains seem to have a linkprofile wich is really killing. Great Designs a lot benefits. What could you do better?
You may get a lot of visits via socials - actually should be somehting possible with that hashtag: #refugees - I don't know how to build a bridge to learn - but google made it with the G-translator - maybe you could brainstorm.
If you like german answers ^^ gplus in my profile + a lot onpage tipps in german on intenseo-blog, but one thing - you chose a pretty hard topic for a SEO Rookie - really. I think you end up pretty sad - you are challenging spiegel-online and a lot of universitys, i-Tunes and playstore. A well known language school just on position 10... Guess they got a lot more budget than you have - just because I saw there TV Ads... really hard topic, tuff competitors - best luck 