你咁寸做乜嘢啫 [－－－－－－－]

Jyutping nei5 gam3 cyun3 zou6 mat1 je5 ze1
Pinyin nǐ gān cùn zuò miē yě zhě

Definitions (CC-CANTO)

why are you being so arrogant / cocky / vain / insolent / provocative? [colloquial]