You might want to deactivate surveys from collecting feedback without having to delete the survey altogether (deleting a survey also deletes the collected responses). 

1. To do this go to Collect and then Surveys tab and choose the survey you would like to deactivate

2. Under each question there is a bar with the option % of respondents will see this question

3. Set the bar to 0% in each question of your survey by clicking on the name of the question one by one, and the scrolling the bar to the bottom until it says 0% of respondents will see this question

4. Add a text saying your survey has ended to the End of survey view (the last view of each survey). Should anyone still open the survey, they will know that the survey is no longer active

5. When you have set the percentage to 0% for each question click on the save icon at the upper right corner of the survey and you are all set!