请帮我改改英语观后感 看过这个杀手不太冷的优先

Watching Leon, a movie that is required in the watching list you presented, is more than a task for me. Actually, during the period of time in high school, I'm not a movie fan because of the limited time and learning tasks. I never believed that there could be a movie, which may change my attitude toward the world or even my life. But then, I met Leon.
The movie gives a setting that killers seems to be born cool. We never know what the fact is, but Leon forced himself to be that way. There was a knocking outside. While Leon opened the door and saw Mathilda, everything was going to change. Even himself didn't realize a hard but colorful new life began. Try to imagine, if only he hadn’t opened the door, his life would be grey as usual; [If only he had fired the shot without hesitation, he wouldn’t trouble protecting the 12-year-old girl wherever she goes.]{Actually, I can't understand what u gonna express...sry.} There are so many 'if-only', but Leon choseto be different. I never know what makes a cleaner say "[we kill]no women and no kids". Maybe a merciful heart, maybe a special experience, or just to be a man.I can't help comparing with those so-called cleaners in the reality. [The fake milk powder makers are far from kind and humanistic, which reveals the fact of the lake of humanity in the real world.]{I can't change because I don't know how to...}
After watching this film, of which there are a few scenes of my special favorite. When Mathilda said, is life always this hard or only when you are a kid, I was lost in thought. It is said that childhood is the happiest period of people’s life. [Without loving parents or even a safe place to live in, Mathilda's childhood was anything but happy.]{sry, I still can't understand...} Sunshine and shade exist in this world at the very same time.[I like this! awesome!] I try to think what in the world Mathilda needed by following Leon. An adulescent girl wanted to be a cool cleaner? or, a child wanted a father. Anyway, her life turns a happy one the moment she was adopted by Leon.
I finished the movie by listening the blue song Rise and Fall.
Everyone's life can be rising and falling, but how to keep balance become a permenant problem.
I thought perhaps, it is humanity that makes the earth what it is today, cruel but wonderful.

{I ganna change the order of something about the rule. also u can check others' comment about this film and change sth properly. i can't guarantee that all the grammar mistakes are corrected, u need check by urself. Hope this can help u.
I like this film as well and sry about typin ENG, Im at university & there is no CN typin.}