You're joking, right?你在开玩笑吧？

You've got to be joking./You're kidding.你肯定是在开玩笑吧

I was completely surprised.我真是大吃一惊

The news came out of nowhere. 这条新闻完全是无中生有

What a surprise.真是意想不到

What a shock.真是令人震惊

I can't believe it.我不相信
That's incredible. 真是令人难以置信


Dialogue1:
A: I've got some good news to share with you. I just found out that I'm getting that promotion that I've always wanted. 我有个好消息要告诉你。我刚刚知道，我终于要如愿以偿获得晋升了。
B: Really? That's wonderful. 真的吗？这可是太好了。

Dialogue2:

A: I was completely surprised when she said she wanted a divorce.当她说她要离婚的时候，我感到很惊讶。
B: You must have been in shock. Let me know if there is anything I can do for you. 你肯定是吓蒙了，要是有什么我能帮上忙的话，一定要告诉我。