Changing font size for text widgets

I can’t seem to figure out how to change the font for the widget headings. I have the simple custom css plugin, I just don’t know what to input. Also, how can I remove the space thats in-between the slider picture and the black bar and how can I make the widgets full-screen width? I’m new at this!

the website is

Hello there,

Front page widget headings font size can be changed with custom css code below (default is 50px):

.panel-grid-cell .widget-title {
    font-size: 40px;

First row have border top of 30px by default, and if you wish to remove that black bar, use custom css code below:

.panel-grid:first-of-type {
    border-top: 0;

I suggest you to check Quill documentation, and to import demo content in order to better understand elements of this theme.

All the Best!