how to get rid of horizontal dividers?

Hi,
I'm trying to customize folio template but I have one problem: on the main page (demo and main too) they are horizontal dividers between menu, modules etc. and I would like to get rid of them but... don'y know how.
I've found these properities in theme.css in "border sections" and when after deleting border properities it works but whenever I click save in customizer those dividers are coming back.
Also tried to delete these border properity from theme.less but again the same thing.

So can someone please can help me and tell me how to get rid of it?
Thank you.

Copy your css code from theme.css, modify it and insert the code into the css/custom.css
After that your custom code will not overwritten again.
www.joomlaplates.com/support/documentation/custom-css-in-joomla