Hello,
If you want to avoid any loss of custom changes and theme options. You must need to use child theme so that your custom code will not lost after update of theme.
So, if you want to install the child theme you do not need to download the child theme from somewhere. Because we already made it for you (you will found in theme package downloaded from themeforest). Here is the link that demonstrate how it works: https://developer.wordpress.org/themes/advanced-topics/child-themes/
For the theme settings you can export all the theme settings. Please go to Theme Settings >> Import/Export >> Click the Export Options button then the file will auto download to your PC when you click the Export Options button.
Best Regards.
.
