it's all Greek to somebody 一窍不通

“一窍不通”，意思是指没有一窍是贯通的，比喻一点儿也不懂（be utterly ignorant of）。可以翻译为“it's all Greek to somebody”，“all Greek to me”是英文惯用语，比喻“something is not understandable”。

例句：

你弄懂这些说明了吗？我根本一窍不通！

Can you make sense of these instructions? It's all Greek to me!

对不起，我不知道你说的是什么，我对那一窍不通。

Sorry, I don't understand what you said. It is Greek to me.