Welcome to the community, @ituhin94! You should be able to validate your XLSForm through this online validator to see if there are any syntax issues in it.
You should be able to learn to create forms in KoBoToolbox through our support page. In addition, to learn more about the XLSForm, you could also visit this site. In addition, this site should also be helpful while creating your XLSForm.
Search for question_name from your survey tab. You should be able to see it somewhere around the expressions used under your relevant or something similar. But unfortunately you have not used a variable name with the same in your XLSForm which has caused this issue. Try fixing this and that should solve your issue.