I would be more than happy to assist you! Please check out my teacher profile and contact me if you want. There is really no need to focus on all the different types of English. Once you know English you will be able to communicate with just about any English speaker anywhere in the world. The main differences are slight pronunciation and slight spelling differences like Americas "color" vs Britains "colour".

Seriously don't worry about speaking British or American English. In truth, there are so many regional dialects and so much cross-cultural sharing because of TV, music, films, books etc that almost every native speaker understands both perfectly. It would be far better to ignore regional differences and simply practice your accent so that it becomes a neutral international accent.

I think that you mean 'distinguish the American from the British pronunciations and tones'. .... rather than English. 'English' is the language common to all of us, whether we're from the USA, UK, Australia or anywhere else in the world!