"know your stuff" in Chinese (Simplified)
很懂行很专业
Definition
指由于有经验或掌握很多知识，某人在某方面非常擅长。人们用这个短语说某人是真正的行家或专家。
Usage Notes (Chinese (Simplified))
属于非正式口语，用来称赞别人，常在你看到某人很擅长某事后说。适用于任何领域，并不是字面意思；不是说只懂“东西”。
Examples
She really knows her stuff when it comes to computers.
她在电脑方面真的**很懂行**。
If you know your stuff, you will pass the test easily.
只要你**很懂行**，考试就能轻松通过。
Our chef really knows her stuff in the kitchen.
我们的厨师在厨房里真的**很专业**。
Don’t worry about the project—he knows his stuff.
别担心这个项目—他**很懂行**。
You can tell she knows her stuff just by the way she talks about art.
光听她谈艺术的方式就能看出她**很专业**。
Wow, you really know your stuff!
哇，你真的**很懂行**！