folowing
Was it Prince of Sahara? It' a small one and fits your description.
https://www.amazon.de/Prince-Sahara-Youka-Nitta/dp/3842025564/ref=sr_1_1?ie=UTF8&qid=1517616575&sr=8-1&keywords=prince+of+sahara
Well its funny but its not the first time that I see something in the store in germany that I cant find anywhere in the web. It looked different from the ones you found but I will have a look anyway, they look interesting. So thank you anyway! ^^
On that evening I also read this one and found it satisfying enough: http://www.mangago.me/read-manga/nessa_no_kusari/
Although this seems to be only one story of several conected and I cant seem to find all of them...
today I walked into a bookstore with a non yaoi friend and without money because I did not want to buy anything and then I saw a small manga that somehow really tickled my fancy... The german title was something with desert in it and also a story like with beduins but it was not Tsuki to Yabanjin. From flipping through the pages I guess it was about a 19 year old boy who somehow got into th desert and in contact with beduins and it was quite explicit... well I did not want to have a closer look because of my friend but now I cant get it out of my mind so it would be really cool if someone here new it (or something alike)