Hello Dear,
I did look at your requirement & I can help you in your project & will be able to fix the code or bug currently which your facing after updating the theme of your WordPress site.
Well, it can be issue of customization which you have made in parent theme.
I must consider child theme for premium themes because by using this method we will not lost our own customization.
So Before Updation, I would prefer to keep backup and then can easily find the customized functions.
Well, I can easily fix the code currently which you are facing & make you sure you will definitely like my work quality.
Please feel free to ask any query, If you have!
Thank You :)