This WordPress Tutorial by WPMU DEV explains how a Child Theme can be made for every WordPress Theme and why you should always do that.
Child themes allow you to modify an existing theme without touching its code. This enables you to update the parent theme without losing your changes.
Once you have created your child theme you’re ready to start implementing some custom changes.
> premium.wpmudev.org/blog/how-to-create-wordpress-child-theme/