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
我不明白你在說什么。
'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發。
I don't understand how the two facts relate.
我不明白這兩個事實有什么聯系。
I don't understand what you're talking about.
我不懂你在說什么。