I don't think so

(a)  

Me da igual. No me importa

(a)  

I don't understand

(a)  

It's not a big deal

(a)  

No es justo

(a)  

No estoy seguro

(a)  

No, thank you

(a)  

No thanks

(a)  

No problem

(a)  

No hay problema

(a)  

No importa

(a)  

No lo creo

(a)  

I can't believe it

(a)  

No me digas

(a)  

I don't care

(a)  

No me sorprendería

(a)  

It can't be

(a)