why not : sie kann naya schwimmen, as gut:good and naya:well
na ja is an exclamation -- it's the "well" in "Well, I don't know what to tell you". It's a bit like "y'know" or "to be honest".
It's not an adverb as in "he can sing well".
thank you very much
why not :: Sie kann schön schwimmen ..
= she can swim beautifully
Can anyone tell me what's wrong with "Sie schwimmt gut"?
That would be "She swims well" and not "She can swim well".