Well one of the things that's irking me is tense issues but also there are a few other things. To point out one "Why do you know that" It would be more proper and fitting to replace "Why" with "How". Overall you did good considering that English isn't your first language. Just a suggestion for the future if you aren't already doing so, but maybe you should try having someone proof read stuff like this for you? Heck even when you know English and you write you can still make a lot of mistakes (I make tons of them).