Hi There,
To remove the border, please add this custom CSS under Theme Options > CSS:
.x-accordion-heading .x-accordion-toggle,
.x-accordion-heading,
.x-accordion-group,
.x-accordion-inner {
border: none;
}
To remove the box shadow, please add this:
.x-accordion-group {
box-shadow: none;
}
If you would like to learn CSS, I am sharing few resources that you take a look to get started with CSS and an interesting tool that you can use to speed up the development process.
I recommend you to watch following video that will help you to get started with CSS.
https://www.youtube.com/watch?v=MFR4WXiLzpc
Sometimes it can get a bit difficult to find out the right selector to be able to write the required CSS codes. A handy tool that can help you in this is Google Chrome dev tools. I am sharing the resource that you can refer to get started with dev tools.
https://developers.google.com/web/tools/chrome-devtools/css/
https://developers.google.com/web/tools/chrome-devtools/
https://www.youtube.com/watch?v=tP_kXBJWPhQ&t=200s
Cheers!