What is the purpose of this essay?
It looks like you are preparing for IELTS or TOEFL. If so, this essay is too short to meet the minimum number of required words. Also, you need to follow the essay structure that they expect. It has to be at least four paras that include Introduction, Two Body Paras and the Conclusion.
It is crystal clear that brain drain is a dangerous phenomenon that prevails in our society.
.... tell briefly why it is dangerous... sounds too vague otherwise
They are several reason which urge highly-skilled people to diffrent place on the world specially developed
This comes as one whole para.... that's two short. You also need to tell what are those reasons
Poverty is one of the major push factors. (have a full stop and break )A lot of people prefer living abroad in order to show their expertise and send some money to their poor family.
A lot of people prefer living abroad in order to show their expertise and send some money to their poor family
.... you need to link with your previous idea;This is the main reason why many people who are qualified and skilled would prefer to go abroad thinking that they can live better lives there.