Hello,
Thanks for using our theme.
As you can read in our docs – https://xstore.helpscoutdocs.com/article/30-base-theme-translation we do not provide a full translation. All pre-created language files have been contributed by our users that’s why the amount of translated strings might vary.
You uploaded translation files of the theme into the correct folder. I’ve synchronized translation, and now you need to translate untranslated strings, that are visible on the frontend, manually.
About the XStore Core plugin, place files into wp-content/languages/plugins folder.
Regards