I don't see where you're coming from.

I don't see your point.

I can't understand what you mean.

我不明白你的意思.

I can't see what you mean.

I don't understand what you're trying to say.

I don't get your drift.

That's how you do it. 所以应该这样做呀

I'm not sure what you mean.

我弄不清楚你想说什么.

I'm not sure I understand.

I'm not sure I see what you mean.

I don't know if I understand what you're trying to say.

I don't know what's what.我不知道这是怎么回事.

I don't have any idea what's going on.

I don't know anything any more.

so, that's the way to use computers.

It's over my head. 太难了，我弄不懂.

It's beyond me.

Your guess is as good as mine. 我也搞不清楚.

How many people live in this town?

Your guess is as good as mine. 你要不知道，那我更不知道了

The more I think about it, the less I understand it. 越想越糊涂.

I don't know what he is driving at.打算做…（我不知道他要干什么）

I don't know what he intends.

I don't know what he is getting at.

I don't know what he is trying to do.

It's not clear. /That's unclear.

That's clear.

What's she after? 她到底想干什么？