Hello,
We have a lot of requests these days, so take my apologies for the delay in answering.
1) Could you, please, provide us with WP Dashboard access to your site and we’ll check what optimization we could do from our side to speed up your store.
2) Read more here about child theme
https://xstore.helpscoutdocs.com/article/32-child-theme
https://developer.wordpress.org/themes/advanced-topics/child-themes/
It’s recommended to use child theme if you plan CSS or PHP changes of theme functionality in the future.
Regards