the manager left his office after he had finished his work

the manager left his office after he had finished his work
为什么是after 不是until\before\if

如果要用until 的话,前面得加一个did not.
until可用作介词或连词,意为“到……时候为止”、“到……时候才”或“在……时候以前不”.什么情况下表达什么意思,关键要看（主）句中的谓语动词是终止性动词还是延续性动词.
1. 如果（主）句中的谓语动词是终止性动词,应采用“... not ... until ...”结构,意为“……到……时候才……”.例如：
You mustn’t eat anything until you see the doctor.
看过医生之后,你才能吃东西.
Don’t get off the bus until it has stopped.
车停稳了以后再下车.
2. 如果（主）句中的谓语动词是延续性动词,那么谓语动词用肯定式或否定式,它们所表达的意思有所不同.
1） 如果谓语动词为肯定式,则until译为“到……时候为止”.例如：
I watched TV until she came back.
我看电视一直看到她回来.
2） 如果谓语动词为否定式,则until应译为“到……时候才”,即“在……以前不”.例如：
I did not watch TV until she came back. （= I began to watch TV when/after she came back.）
直到她回来我才开始看电视.
这句话中left 就是终止性动词,所以用until 的话,前面得用否定形式.

好好学习下