Reduce Prefooter Height

can you provide a url?

I have the same question. I only have one line of text, and box is way to high.
You can see it here. https://ydot.dk

#footer {
  padding: <strong>24px</strong> 40px;
}

Adjusting your first padding should shrink the size.

Please use a child theme though!

Both #header and #footer have min-height set to 100px.
You could add this code via My Custom CSS plugin to shrink the footer:
#footer { min-height: auto; auto; }