Hello, Paivi
Translation files of the theme should be placed in /wp-content/languages/themes/ folder,
plugins, like Core plugin, in /wp-content/languages/plugins folder
with correct names, for example, xstore-ar.po for the theme and xstore-core-ar.po for XStore Core plugin, then you will not lose translation after the update – https://www.8theme.com/documentation/xstore/theme-translation/base-theme-translation/
We would recommend doing a backup of all the files before any update.
Also, after every update, you need to synchronize translation – https://www.8theme.com/documentation/xstore/theme-translation/translation-files-update/ Sometimes new strings are added, and only after synchronization, you’ll be able to translate new strings or strings that were changed. Not always, but some strings can be missing after the sync and you need to find and translate them one more time, this is independent of us and relates to WP functionality.
Kind Regards,
8theme team