Hello,

That’s why we always recommend to take a complete backup of the website before updating the theme.

It happens when you make all the changes to the parent theme. We always recommend making the customization to the child theme then you will not lose them while updating the theme.

So you need to make all the customization to the child theme. Then take a complete backup of the website and update the theme. You will not lose your customization.

Best Regards.