a rough diamond	a good person with uncivil manners
golden boy	successful/popular person
pull sb’s leg	tease sb
put on a brave face	try to look happy in order to hide embarassement
stab sb in the back	to be disloyal
make sb’s hackles rise	make sb very angry
behind one‘s back	without one's knowledge
get hot under the collar	annoyed/frustrated/excited/worried
keep one’s cool	remain calm in difficult situation
down-to-earth	practical
get sth off one’s chest	talk about worries in order to gain relief
a nosy Parker	sb curious about other's business
a dark horse	sb whose character is unknown
lose one's head	lose control
have a chip on one's shoulder	sense of anger because of unfair treatment
have a short fuse	someone who easily gets angry
get one’s own back	take revenge
a wet blanket	person who doesn't like others to have fun
as straight as a die	hinest person
take sb‘s point	acept/appreciate what sb has said