There is a lot of run-on sentences in this essay. I tried to have a go at correcting some of it but that didn't pan out too well. First things first, separate your clauses appropriately and take a good look at your grammar.
For example:
As an international student, Northwestern University caught my eye when I saw that their international undergraduate enrollmenthas been continuing to experience increases. Then, I researched about it and got to know about their prestige and reputation and,getting a clear vision that this school will be the best for me.
The rest of the essay is littered with mistakes. Apart from the writing problem, you mentioned prestige too many times. Your case of wanting to go into northwestern is simply not strong enough and by beginning with the fact that you noticed them by looking at their international student enrollment rate will make them think that "Oh, this kid wants to get into this school just because apparently its getting easier to get into it as an international applicant" which is a terrible impression. Plus, you did not really mention any specific detail about the engineering school of Northwestern at all.
It really needs a lot of work.