You can simply install WCleaner on your device it requires Android 2.3 and up. After the installation tray will open. Here you can see the number of files stored under various categories like the wallpapers, profile pictures, images, audio files, voice notes, videos and the backup files.
You can tap on each of these categories to see a full list of files belonging to that category. You can also tap on the bin icon next to each of these categories to delete all the files belonging to that category. If you want to delete all files just tap “Delete All” button.

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