"border of a pizza" === "crust"; if you can watch american news broadcasts, those help, they are geared towards the average native speaker. there are websites you can go to and find a speaking partner, you help someone who knows english and wants to learn german and they help you, via something like skype.

other than complete immersion it's difficult to learn and even within america things are said differently in the North east/new england than they are in the "South"