The app is not able to delete anything by itself. When you tap the Quick clean button, the review screen lists all of the item types that can be cleaned. There are two categories: "Unneeded files" (truly dispensable data) and "Files to review" (data that may or may not be valuable to you). We recommend reviewing these items. More on our FAQ site.
Thanks for sharing your thoughts! We appreciate your feedback. Ads are necessary for us to keep the app free for all users. However, you'll be glad all ads are skippable after just 5 seconds. If you prefer an ad-free experience, consider upgrading to our premium version. Let us know if you have any other questions or concerns! Hector*AVG