I have to learn
I had to learn
did the assignments and projects
what kind of assignments and projects?
Also, take out the "had to" and say: "I learned, or I did". This way, it doesn't make you sound like you HAD to do it without any choice.
While this meant additional work
what meant additional work? school lessons? how is that additional work?
And I had to help System study and program design. I am very interested in System Design and programming very much.
I had to help System study and program design and I became very interested in those disciplines.
at your university.
at XXX university, avoid using your's
I think that you should parse your essay into paragraphs, so that it doesn't read like a huge paragraph. Have an intro and a thesis that tells the reader what you're going to talk about. Overall, I think it's a pretty good graduate essay, considering English isn't your first language.