How to get google adwords data using google analytics api?

I was trying to integrate a web application with google analytics. I successfully integrated but when I was trying to get google adwords metrics ga:costPerConversion and ga:ROAS , I was getting incorrect data.

I am unable to fix this issue like why the api data not matching with google adwords dashboard data?

It will be great if anybody could help me with this issue?

Is there any metrics or way to get the total conversions of a google ads??