You can delete files, except for contacts, from Send Anywhere app.
1. Select the files you want to delete.
2. Tap ( ⋮ ) ellipsis icon next to Send button at the bottom.
3. Tap Delete.
※ Files in Photos and Videos tabs are stored in the Recently Deleted of Photos app for 30 days before being deleted.
※ Please note that once you delete files in Files tab, you cannot recover them anymore.