to get a big head 极度自负(成语)
To get too high an opinion of one’s ability, power, or importance; to become arrogant.
例句
After his promotion at work, the young man got a big head and started telling everyone he was much more talented than the boss.
在得到晋职后,这位年轻人变得极度自负,开始逢人就说,他的能力远超过老板。