.column .widget {
border: 1px solid rgba(204,204,204,1);
}
That looks like the code that creates the borders on widgets.
Normally when you change the style of a theme you create what is called a’child theme’ first and then make the changes in that. If you just make changes to the theme directly without making a child theme first, any changes you make just get overwritten when you update the theme. So you might need to learn how to make a child theme going forward or get someone to do this for you.
But aside from the above, basically you need to find that code in style.css and change the 1px to 0px and the widget border should go away. If that were the only change you were going to make then maybe maybe it might be OK to do this change in the editor in the Admin but be warned it’s not usually the recommended way to go about it (because… your borders would come back when the theme is updated and that code overwritten).
Hope that helps!
