This app was mentioned in 5 comments, with an average of 1.80 upvotes
I would download file manager, and then use the option to scan your devices to find the biggest files in your phone. Once you found files that don't fall into any category (misc), you decide then if you want to delete them or not.
samba接続も出来るので、これつかってます。
Wait.. You can still get the HD version o.O - https://play.google.com/store/apps/details?id=com.rhmsoft.fm.hd&hl=en
For a File Manager, I've been using File Manager HD https://play.google.com/store/apps/details?id=com.rhmsoft.fm.hd