Resources for learning Cantonese
I agree with others who say you should work with a native speaker to help you with pronunciation. However, having a grammar book will be immensely helpful as well, since many native speakers are often unaware of their own language's grammar (many will often say "that's just how you say it" without knowing why; I've also heard native speakers assert that Cantonese doesn't have grammar).

For this, I recommend the series of books by Virginia Yip and Stephen Matthews. Basic Cantonese and Intermediate Cantonese are very good in my opinion. They also have a more comprehensive reference that covers almost any question you may have about the intricacies of Cantonese grammar; it would be an excellent study companion.