Talk to them with a smile on your face and don't pretend you understand something when you actually don't. It's better if you ask them. If you find a group that seems to understand your difficulty in communicating, try hanging out with them and be friends. You'll learn faster when you're having fun.
Also, a piece of advice, watch a lot of TV (in English). Just be sure you're watching good shows. Cartoons should help a lot ^^