Making the gap smaller

Try the CSS

#BB_BuyButtonForm br{
 display: none;
}

Where in the stylesheet should I put it? I put it in a random place and it isn’t working

Are you using a custom or child theme, or do you have a custom style/css plugin?

It is a custom theme that I downloaded from www.ads-software.com

You may need to create a Child Theme or use a Custom Style/CSS plugin to modify your theme.