我不明白用英文怎麼表達?

I don't understand the instructions.

我不懂這些指令的意思。

I don't understand what you are talking about

我不明白你在說什麼。

'I don't understand,' the Inspector mumbled, passing a hand through his hair

“我不明白,”巡官一邊嘟囔道,一邊用手捋了一下頭髮。

I don't understand how the two facts relate.

我不明白這兩個事實有什麼聯繫。

I don't understand what you're talking about.

我不懂你在說什麼。