I'm not familiar with this movie, but it sounds interesting. "Murphy's Law" usually means that anything that can possibly go wrong will go wrong. It's kind of a joke-concept. It means that everyone is guaranteed to have bad luck. When you said, "I sympathized this law," what did you mean? To "sympathize" means to feel what another person is feeling. I haven't seen the movie, so I don't know how "Murphy's Law" was used in it. Did you mean to say, "I understand this idea of 'Murphy's Law'" or something like that? Perhaps you "appreciate" the concept. A popular way to say this in English is, "I can really relate to the idea of Murphy's Law." ("I can relate to . . ." is not very good English, but it's a popular expression, and many English speakers use it. It means that you can sympathize with an idea).