Hello,
To update the theme you can create a staging site (a full copy of live site) and update xstore there. Then, if everything is ok, update the production site.
https://youtu.be/I7wPeHEPb6E
XStore 4.0 and 5.0 are major updates and we have changed a lot of things https://xstore.8theme.com/update-history/ including theme styles https://preview.themeforest.net/item/xstore-responsive-woocommerce-theme/full_screen_preview/15780546 For example, Simple header type, that is using on your site with 3.16 theme version, was removed in 5.0 version of the theme.
Also, if you use child theme then child theme files should be updated according to new files.
Setup Wizard should be skipped after the update.
https://www.8theme.com/documentation/xstore/theme-installation/theme-update/
https://www.8theme.com/documentation/xstore/plugins/plugins-update/
We can help you with the update. Provide temporary wp-admin and FTP access to the staging/test site.
Regards