Thank you so much. 

非常感谢

Thanks a lot. 

多谢

I can't thank you enough for this.

感激不尽

I don't know how I can thank you.

真不知道怎么感谢你。

I really appreciate this. 

真的太感谢你了。

Dialogue1:

A: Thanks. That was really nice of you.

太感谢了，你真是太好了。

B: No problem, happy to help. 

没什么，很高兴能帮到你。

Dialogue2:

A: Thanks a lot.

多谢。

B: You're welcome, I'm glad you like it. 

不客气，很开心你能喜欢。

Dialogue3:

A: I don't know how I can thank you for this.

我真的不知道我该如何谢谢你。

B: That's ok. Don't mention it.

没什么的，不必再提。

Dialogue4:

A: I really appreciate this.

我真的很感谢。

B: It's nothing. 

没什么的。

Conversation:

A: I really want to thank you for all of your help. 

真是太感谢你提供的帮助了。

B: It was nothing, really. I'm sure you would have done the same for me. 

没什么了，真的，我想你也会为我这么做的。

A: Still, you took a lot of time out of your day to help me with this presentation. You didn't have to do that. 

你花了那么长时间，帮我准备这份报告，你本不必这么做的。

B: Yeah, but when I first started here, you went out of your way to make me feel welcome. I really appreciate that. 

是的，但是我刚来的时候你竭尽全力让我感到很有归属感，对此我真的非常感谢。

go out of one's way表示“竭尽全力”

A: Well, I'm glad we could help each other out. 

我很高兴，我们可以相互帮忙。