I am confused by the two sentences written below.  I dont get why it has nasıl at the start but also the question suffix on the end ? 

nasıl güzel dans ediyormusun

Already got some help from lovely Yersu and Upsy so no need to answer

I would appreciate the explanation also

it is like, "tell/show me, do you dance well ?"

Açıklaman için teşekkür ederim

I think it needs a comma:

Nasıl, güzel dans ediyor musun?

How, do you dance well?

They said in the context I explained that it meant like

Say! do you dance well/   ehh !, do you dance well

 Say! Do you make nice food ?

Obviously it does not mean say literally but in the way we use it in english sometimes

There is no actual HOW in the sentence. It did not make sense in the converstaion I was having to ask, How , do you dance well ?.

it is a matter of emphasis.

here the word "nasil" is pronounced in a different way.

 I think it resembles when we say in English:

How well do you dance?

or How well do you cook (make food)?

it isnt neccesary to use ´´nasıl´´

in common ; nasıl qualifies and asks adj