Hi @forum80,
If you have a customized file in Child Theme then that customized files will always override the Main theme and we have noticed that you added customized style properties to style.css file in your Child Theme. You have also made change to the layout width though the theme already have the narrow layout option.
To make the layout full width Please go to the style.css file of the Child Theme and remove the below mentioned code that you will find on line no: 52.
/* max-width: 90%; */
Thanks