Our App is already live to Google Play and we would like to move to Mhgdesignagency, what is that Mhgdesignagency needs from us in order for smooth transition?

In order for you to transfer your existing Live App on Google Play to Mhgdesignagency, You need to provide us with your Apps original keystore and private key, however If your app is published to Google Play and  you know longer have key with which you signed your app, you will not be able to publish any updates to your app unless you unpublish the current app  and publish a new app but this would mean you will lose your existing app users, ratings & reviews of  your app.