给我比较下“不用谢”和“没关系”？

表示不用谢:
You are welcome!
Not at all!
Don't mention it!
It's my pleasure!

表示没关系:
That's all right!
It doesn't matter!
That's ok!

都一个意思。

都可以

You are welcome! Don't mention it! It's my pleasure!是不用谢
That's all right! Not at all! It doesn't matter! That's ok! 是没关系