Hello,
Regarding your query related to the customization, you should not make any modification directly in your parent theme as all of the customizations will be lost upon update to the latest version of the theme and the same situation is here when you reinstall the theme.
So please go through the child theme for the changes and shift all your customizations in the child theme before you uninstall the theme. You can refer to the below-given documentation link to get detailed assistance on how to create a child theme.
https://wptravel.io/how-to-create-a-child-theme/
Hope this helps.
If you have further queries, let us know.
Regards.