Hello,
Thank you for reaching out to us with your query. We understand your concern about changing the theme without losing the existing data on your website.
Please be aware that if the previously installed demo content is not removed, there is a possibility that the new demo version may not be installed correctly on the existing site. We recommend performing a test on a staging site by creating a full copy of the current site.
Another solution can be using XStore Studio which allows to import sections from different demos https://www.8theme.com/documentation/xstore/xstore-features/xstudio-feature-of-xstore-wordpress-theme/
We hope this information is helpful.
Best Regards,
8Theme’s Team