空前绝后unprecedented and never to be duplicated;the first and the last;unmatched;unique

口是心非saying something that one does not mean (lit. mouth says yes;heart no)

口说无凭oral expressions can not be taken as evidence;words of mouth alone don’t carry conviction

苦尽甘来bitterness finishes;sweetness begins;the hard times are over;the good times just beginning

滥竽充数fill a position just to make up the number (lit. to play the yú 竽 mouth organ to make up numbers)

狼狈为奸villains collude together;to work hand in glove with sb.

狼吞虎咽to eat very quickly and ravenously

老马识途an old hand is a good guide;an experienced worker knows what to do

乐不思蜀indulge in pleasure and forget home and duty

乐此不疲to enjoy sth and never tire of it