Uploaded file can be deleted by the member who uploaded or the Team Admin.
1.Select the file you would like to delete and click […]-[Delete].
1. Go to details of the file you would like to delete and tap […]-[Delete].
However, comments will still remain undeleted so later on, other team members can understand work history and workflow. If you want to delete the comments as well, person who commented has to delete it him/herself.