whats the easiest and fastest way to learn and understand Polish??
Be born in Poland to Polish parents.
I would give a better answer, but the best I can come up with is the usual:
Try to meet Poles who can only really speak Polish (easier here in the UK than in Australia, I can be fairly certain).
Get a good book that goes through all the grammar.
Play with PolishForums dot com - the forum for all your Polish needs!