tu peux dire aussi: No, para nada. mais ça depend du contexte. par example , parle toi chinesse? no, pas du tout. ¿hablas chino? No, nada de nada. ou No, nada. no, en absoluto. et il y a des autres expresions, mais ça depend de que est-ce que vous voulez dire...

I guess you meant this: Es muy costoso(It's too expensive) = not at all. In spanish it would be "para nada" / "en lo absoluto" In the previous answer.. gracias(thanks) not at all = de nada.. but isn't it more like "de rien" rather than "pas du tout"? do you answer to merci with pas du tout? D;!

Am I childish? Not at all!! = No, en absoluto!!. No, de ninguna manera!!

thank u. :) now i must revealed that spanish is hard to learn but don't worry i will learn till i get it. i need patience for this hard mission. but thank u anyway. :)

By the way Its not "en no absolute" It might make more sense to add the no haha, but It's "en lo absoluto", I answered your comment among other things in my answer :P!