Get ride of so much white space

Hi there,

https://www.popspotsnyctours.com/

I like Gateway overall but there’s a ton of white space. Too much white space in the menu bar, too much white space between the featured blog posts and the blog header, and too much between the end of the featured blog posts (Greenwich Village – Rock & Movies) to the Front Page “Walk in the footsteps of legends”. There’s even a ton of gray space at the top of the footer where the widgets are.

I found the CSS below to start with the menu, but it didn’t change anything when I pasted it in. Can someone please help?
.site-content {
margin-top: 4.5em;
}