Hi Heike,
I think the best choice would be Dipl.-Med. Abdallah Karajoli. He works in Meoclinic, Friedrichstraße 71, 10117 Berlin. His website: ****://***.kinderarztkarajoli.de/ and his number: +49 (0)30 2094 4000
There is another pediatrician speaking arabic but unfortunately not in Mitte or Prenzl Berg. I will write her address below.
Majd Maarouf
Oranienstr. 155 - 158
(U-Bhf. Moritzplatz)
10969 Berlin - Kreuzberg
Tel.: 030 - 614 16 19
****://***.praxis-dr-maarouf.de/kontakt.html
Hope that will help. Good luck to the little guy :)