一窍不通

They have little acquaintance with colloquial English.

他们对英语会话几乎不通。

I’m afraid geophysics is rather a closed book to me.

我对地球物理学不通。

Don’t ask him to organize things! He doesn’t know his arse from his elbow!

千他来组织，他不通。

It's a sealed book to me.

我对不通。