What does 谈晋倏忽之间勾了下嘴角 mean?
哦？”谈晋倏忽之间勾了下嘴角，“金主让你做什么就做什么，是这个意思吗？”


倏忽之间: suddenly

For 勾了下嘴角 you could perhaps write: 轻蔑 or 冷笑 

谈晋倏忽之间勾了下嘴角，
Tan Jin suddenly snarled,

“金主让你做什么就做什么，是这个意思吗？
"If the boss wants you to do then do it, is that what you mean?"

You could replace 倏忽之间勾了下嘴角 with either: 冷笑道 or 轻蔑地说道

谈晋冷笑道， : Tan Jin, with a sarcastic smile, said,
谈晋轻蔑地说道，Tan Jin disdainfully spoke,