I would like to know how to fix Arabic font on Samsung Galaxy s2.
By fixing, you mean adding it? There are quite a few tutorials on the Internet about it, here are some examples:
http://www.ce4arab.com/vb7/showthread.php?t=330824
http://how2q8.com/2011/06/30/how-to-add-arabic-to-samsung-galaxy-s2-arabic-software/