Hi, yes of course you can, that's one easy method to learn a language. I'm doing the same right now learning Chinese, just watch 1 or 2 hours of Chinese show or movies everyday and getting better everyday. Watching movies is a great method because you can associate their expression to the words you're learning. However I think it'd be best to sometimes mix it with other methods such as grammar learning, etc.
I believe using mix methods is the best way and quickest way to learn a language (at least for me !)