Can someone explain to me this expression I heard from a friend?
¡Ni qué buenas ni qué nada!
Thanks for your help.
In Spanish there are some expressions to show disagreement with something previously expressed. In this link you can search for the expression ni qué ocho cuartos, used in a very similar way to what you heard:
¡Qué buenas ni qué ocho cuartos!
Another similar expression is ni qué niño muerto:
¡Qué buenas ni qué niño muerto!
Probably, the day you said "¡buenas!" (or maybe "¡buenas tardes!") to that person, there was a bad weather, or maybe that person was not having a good day at all, so he/she just showed disagreement (maybe in an angry way). The expression ni qué nada is similar to those mentioned, just shorter.