Blank space

This CSS:

section.page-title-section.bg-secondary {
    padding-top: 1em;
    padding-bottom: 1em;
    height: auto;
}

To add or override CSS: use the “Additional CSS” option in the customizer. https://codex.ww.wp.xz.cn/CSS#Custom_CSS_in_WordPress

Learn to use the Chrome Developer Tools to help you see and test changes to your CSS.

If you want that gone entirely, use

section.page-title-section.bg-secondary {
   display:none;
}