HI
The child theme offers the safest and easiest way to modify an existing theme. Yes child theme update won’t be changes your customization after parent theme update unless you update child them as well. We are also sharing theme update and child theme documentation with you for your better understanding.
https://xstore.helpscoutdocs.com/article/32-child-theme
https://xstore.helpscoutdocs.com/article/63-theme-update