Hi Vineet,
You can just take the xml from above from <Deal> to </Deal> and put it in test button by replacing the dummy <Deal> to </Deal> and keeping everything as it is, and go to tree view, if it is not showing any red marks, then the payload which you have given is matching with the structure you have defined.
From this, you can see the xml coming from 3rd party is matching with the structure you have defined.
Regards
Vishnu