This sounds like you have made quite a lot of changes or added your own php coding in your child theme’s php files?
Sorry, custom coding on this level is outside the scope of support for the theme – minor CSS modifications and help with the theme options/functionality.
We would effectively be developing a new bespoke child theme for yourself which would would require custom coding and testing, and an option would to maybe find a reputable freelance WordPress developer on Upwork for this kind of custom service.