Q: Is there a way to retrieve update of WordPress core & WooCommerce translation files (or will this be done using the normal update screens? or should I do that myself by downloading and FTP?)
A: WordPress and Woocommerce translations are updated with the regular core updates. No action is needed from you.
But don’t forget to update translations on page “yoursite/wp-admin/update-core.php”. ​It is easy. Sometimes it helps.
Useful link: How to install Woocommerce language pack.
WooCommerce Language Packs
Projects > Plugins > WooCommerce