If you want to customize core file ,you can simple copy and paste the core file/template and paste it on child theme. For this make sure you are following same directory. For example. let say there is example-parentfile.php inside extras folder, then to customize this file you need to keep same file creating new folder called extras
And regarding to hide article information , we had look over your screenshot and found that the css given to hide article information is not added on style.css file of child theme. So please add this css on child theme style.css file to fix your issue.