This error occurs if the file or folder has incorrect permissions. To restore the rights to folders, you can either use an FTP client, which provides the ability to change the rights to files.
For files and folders that cannot be deleted, you must set the rights to 755, after which you will be able to delete the data.
These rights give permission to the owner of the file to read, write and execute (rwx), that is. full access. For the owner group and other users, these rights give the ability to read and execute the file (r-x).