Hi this website may be useful for you. http://www.italki.com/knowledge/contribution-English+essay+topics+for+students.htm

I can tell you how You must read a lot of English if you really want to improve you writing ability And trust me on that

To write well we have to read a lot, so we learn vocabulary, phrases, grammar, etc.

read a lot .. after time you will always remember words in your mind .. this is the best way !

get a good book that you enjoy and read it a lot! don't be so hard on yourself , you don't really need to study all the time, enjoy your lecture and your brain will do the rest fo you!