Thanks for the response.
I managed to get it right. there was a conflict with another plugin that does translation.
But now I have another problem.
before I log in, the form is shown in English.
But when I log in, then i can see the arabic translation!
Also some error messages seem wrong. Maybe an error in the PO file that I used. I opened one of the PO files in lang folder and translate it. Is there a latest version or the original file so I can update the translation?
Thanks for the support.
Wesam