We suggest you to try using this plugin: Loco Translate. It can be used for changing default theme labels and messages either.
4) if you need to edit strings related to The7 post types (portfolio, albums, etc.), you should refer to Loco Translation -> Plugins -> The7 Elements.
If you want to completely remove a label, you should simply replace it with an empty string.
If the translation doesn’t work or some words cannot be found, make sure that the site has only one copy of the theme installed and then press the ‘Sync’ button in the Loco Translation page.
It is really helpful!