打肿脸充胖子 (dǎ zhǒng liǎn chōng pàngzī)
do sth. beyond one's ability

【释义】要面子，硬撑着做力不能及的事。
To get the respect and attention from the others, some people just pretend like the rich, some of them even slap their face until it’s swollen in an effort to look imposing.
Chinese use this expression to criticize those who have no certain ability or enough money but still try means to be like the rich.

【例1】
A：我想请朋友去五星级饭店吃饭。
I want to treat my friends at five-star hotel.
B：不要打肿脸充胖子。
Don't do that beyond your ability.

【例2】
A：听说他结婚时，为了炫耀，问别人借了很多钱。
It's said that when he got married, he borrowd a lot of money in order to show off.
B：他这个人总是喜欢打肿脸充胖子。
He always did like this to pretend to be a wealthy man.