sherouk,
Yours is a good question and the photos are excellent. Thanks to you I have done some quick research and have learned that most of the world's basil is grown in Egypt!
I agree with
@william that you might want to add a diluted liquid fertilizer.
Are you growing to save the seeds for replanting? or to use the leaves in cooking? If you are not attempting to save seeds you could pinch off the flowers to encourage new leaf growth.
