pls tell me proper use of DI and CI

use of LE SO NOW I MUST SAY LE IS JUST USED LIKE PAST TENSE AS IN ENGLISH

please explain me use of " LE " , waiting

please tell me different between use of ER and LIANG ,waiting

golu's notebook entry: Jul 13, 2010 你好吗我的朋友 你们忙吗 你好你的家人 我在商店 我不忙，你呢