Hello,
Please read this article – https://xstore.helpscoutdocs.com/article/30-base-theme-translation and create translation for XStore theme. Make sure that translation files are placed in /wp-content/languages/themes/ folder.
About XStore Core plugin translation, you need to Sync it – https://xstore.helpscoutdocs.com/article/103-translation-files-update , then find and translate new strings. Also, synchronize translation for WooCommerce plugin.
Regards
