不知天高地厚
bù​zhī​tiān​gāo​dì​hòu

to have an exaggerated opinion of oneself

不知天高地厚 bù​zhī​tiān​gāo​dì​hòu
to have an exaggerated opinion of oneself
to be arrogant and overestimate one's own importance or abilities
to be unaware of the world's complexity
to be naive or ignorant of the difficulties and complexities of life or a situation