Copy the theme files you changed to your local computer to save the changes you made. Then reinstall the parent and child theme.
Then make the changes to the child theme that you made in the code of the parent theme. Normally, if you want to change code, you do it via a child theme. THat way, the changes you make to code/CSS/whatever will not be overwritten with a theme update.
Not sure how the included child theme will fit into this. If the theme author is using the Child Theme protocol properly, a theme update will only affect the parent theme.