You can classify your responses in 4 different groups as Thank you, Complaint, Proposal and General.
Select All Feedbacks from the menu under the Responses tab. If the Classification column is not visible, click on the Columns button to make it visible.
It will be automatically saved when you change the classification in the corresponding row.
Alternative method
Select All Feedbacks from the menu under the Responses tab. If the Edit column is not visible, click on the Edit button to make it visible.
Click Edit button to open the following screen. On this screen, select Classification and click the save button.