I've always had difficulty pronouncing the letter /r/. Whenever i try to say /r/ it comes out as a gha, a sound similar to the arabic letter غ. Any idea how i can fix this?
I suggest you temporarily (or permanently, if things don't work out) replace the R with a different sound that you can comfortably produce, and which people will understand. Here are a few possibilities:
a Spanish R
a French or German R
Just remember that people from all over the world can be understood pretty well, despite pronouncing the R in their own way.
-- Edit -- Experiment with a variety of foreign-sounding R sounds in your English, and see which one appeals to you most.
I'm not a speech therapist, but my guess is that a good word to try to get a real R in would be something like fur.