If you have modified theme files, they will be lost unless you move the changes to a child theme –
http://codex.ww.wp.xz.cn/Child_Themes
If you have only made changes via the theme settings/options, those won’t be overwritten.
I made the changes in the styleSheet file
Should I copy it or duplicate it in the child-theme folder?
Thanks a lot!
Ideally, a child theme style.css file should contain only changes – as copying the entire file creates duplicate code and makes it much harder to keep track of what you have changed. A file comparison tool like http://www.diffchecker.com/ may be helpful in locating your changes.
Whatever you do, be sure you have backed up your site before updating anything :).
