Hello,
Translation depends on the folder where you placed it. If you placed translation files in the xstore/languages http://prntscr.com/stjcuq then you will lose it after the update because the system removes the theme folder and unzips the new one. In the readme file inside languages folder, in theme documentation https://xstore.helpscoutdocs.com/article/30-base-theme-translation we clearly ask to place translation to wp-content/languages/themes So, move your translation to Custom or System folder http://prntscr.com/stje7x if you don’t want to lose your translation again.
Regards