我們換個話題吧!

Let's change the subject.

Let's talk about something else.

Let's talk about something different.

I'd rather talk about something else.

言歸正傳。

Let's get back to the subject.

Let's get back to the point.

Let's get back on track.

我現在不想談那件事。

I don't want to talk about it now.

I'd prefer not to talk about it.

Let's talk about it later.

We're playing golf this Sunday, right?

另外我們說說……

To change the subject...

I can't believe it.

好了，玩笑就到此……

Well, all joking aside,...

Ha, ha, that's a good one!

Well, all joking aside, let's get to work.

Well, seriously,...

順便提一下……

By the way, how is John?

Well,...

Now,...

你剛才說什么來著?

You were saying? *說話過程中話題改變時。

Continue. Carry on.

Please go on.

啊，我想起來了。

Oh, that reminds me. I can't go. (啊，我想起來了，我去不了。)

別說了。

Let's stop talking.

I'm tired of talking.

I don't want to talk anymore.

那事兒我聽過了。

I've heard the story before. *用于對方重復說一件事時。

You've already told me.

I'm sick and tired of hearing that. *sick and tired of... “對……膩透了”。

I've heard enough about it (already).*加already起強調作用。

I don't want to hear about it anymore.

這件事別再說了。

Let's drop the subject. *drop 除了“落下”之外，還表示“(問題、事件、話題等)完了、結束、停止”。

Let's drop it.

I don't want to talk about it anymore.

別那么大聲說。

Don't say it so loud.

I thought you were hard of hearing.

Don't say that kind of thing so loudly.

(Please) lower you voice.

（來源：網絡）