1.I don't understand.
我不明白。

2.I'm not following.
我有点不明白了。

3.I'm confused.
我有点晕。

4.I don't really understand.
我不太明白。

5.I don't have any idea what's going on.
我压根不知道是怎么回事。

6.It's over my head.
太难懂了。

7.It's beyond me.
我完全不能理解。

8.That's not clear.
我不清楚。

9.I can't see your point.
我不明白你在说什么。

10.I'm not sure what you mean.
我不明白你的意思。

我还知道一个，，
I don't know.

I don't understand. 我经常说这句的~~~

thanks for sharing