?我们换个话题吧!?

Let's change the subject.
Okay, okay, I'll pay you back next week... (好吧,好吧,下星期我还你钱……)
Let's change the subject. (那,我们换个话题吧。)
Let's talk about something else.
Let's talk about something different.
I'd rather talk about something else. (能不能换个别的话题。)?

言归正传。?
Let's get back to the subject.
Let's get back to the subject. (言归正传。)
Yes, let's. (对。)
Let's get back to the point.
Let's get back on track.

我现在不想谈那件事。?
I don't want to talk about it now.
I'd prefer not to talk about it. (我不想谈论那件事。)?

那事儿以后再说吧。
Let's talk about it later.
We're playing golf this Sunday, right? (我们这个星期天要去打高尔夫球,对吧?)
Let's talk about it later. (那事儿以后再说吧。)?

另外我们说说……?

To change the subject...
I can't believe it. (真让人难以相信。)
To change the subject... (另外我们谈点儿别的吧。)?

好了,玩笑就到此……?
Well, all joking aside,...
Ha, ha, that's a good one! (哈,哈,这个玩笑真有趣。)
Well, all joking aside, let's get to work. (好了好了,玩笑归玩笑,快去干活儿吧。)
Well, seriously,...?

顺便提一下……?
By the way,...
It was really fun. (真的特好玩。)
By the way, how is John? (顺便问一下,约翰怎么样了?)
Well,...
Now,...?

你刚才说什么来着??
You were saying? *说话过程中话题改变时。
Continue.
Carry on.
Please go on.?

啊,我想起来了。?
That reminds me.
The party gonna be great! (那个舞会一定会很棒。)
Oh, that reminds me. I can't go. (啊,我想起来了,我去不了。)?

别说了。?
Let's stop talking.
I'm tired of talking. (我都说累了。)
I don't want to talk anymore. (我不想说了。)?

那事儿我听过了。?
I've heard the story before. *用于对方重复说一件事时。
You've already told me.
I'm sick and tired of hearing that. (我耳朵都听出老茧了。) *sick and tired of... “对……腻透了”。
I've heard enough about it (already).*加already起强调作用。
I don't want to hear about it anymore. (我再也不想听那件事了。)

这件事别再说了。?
Let's drop the subject. *drop 除了“落下”之外,还表示“(问题、事件、话题等)完了、结束、停止”。
Let's drop it.
I don't want to talk about it anymore. (我再也不想说那件事了。)?

别那么大声说。?
Don't say it so loud.
Don't say it so loud. (别那么大声说。)
I thought you were hard of hearing. (我以为你没听见呢。)
Don't say that kind of thing so loudly. (那种事别那么大声嚷嚷。)
(Please) lower you voice. (小点儿声。)