How to create a child theme after you hace done changes in the parent theme?

Hello, I hope you have a wonderful weekend;

We are beginners and we have done changes in the theme without doing a child theme first. Now we have viewed the theme update and don´t want to lose everything done.
After read this: “Child Themes « WordPress Codex”, we know how to change de style.css and functions.php in case of create a child theme from a new unmodified parent theme but we don´t understand how to Create a Child Theme from a Modified Existing Theme like the tutorial explains, could you help us?

Hi @lacasarevuelta,

I hope you are well today and thank you for your question.

You have to remove all the changes made in the Activello parent theme and make it in the child theme.

If you are not a developer then you can consider hiring a developer to develop it for you. You can hire a developer from any freelance site. Colorlib recommends the developer

Best Regards,