"know your shit" in Chinese (Simplified)
很懂行（粗俗）- 真内行（俚语）
Definition
表示某人非常精通或擅长某事。这是一个非正式且带有粗俗用语的表达。
Usage Notes (Chinese (Simplified))
极为口语化且稍显粗俗，仅限熟人之间或非正式场合使用。表达很懂行并自信。不要在正式或工作场合使用。更常见、更委婉的说法有'know your stuff'。
Examples
He really knows his shit when it comes to computers.
他在电脑方面真的**很懂行**。
If you want advice on cars, talk to Sam—he knows his shit.
想要关于汽车的建议，去找Sam吧——他**非常懂行**。
She knows her shit in marketing.
她在市场营销上真的**很懂行**。
Don’t worry, our guide knows his shit—we’re in good hands.
别担心，我们的导游**很内行**，我们很安全。
Wow, you really know your shit about wine!
哇，你真的**很会选**葡萄酒啊！
Trust Jamie for this project—she knows her shit.
这个项目找Jamie没错——她**非常内行**。