Jessica G.

Can you post a link to your site? That will help folks be able to diagnose the cause.

Can you post a link to your site?

The content on the right is coming from the sidebar. If there’s an option for a full-width page template, selecting it should keep the sidebar from appearing. You can also go into Appearance –> Widgets, open the main sidebar, and delete the text block, if you don’t want it to appear on any other pages.

For the page tabs: did you set up a menu under Appearance –> Menus? Or is it displaying the default menu (all pages)?

Can you share what theme you’re using, or post a link to the site in question?

Did you create your child theme by hand or by using a child theme installer plugin?

Can you post a link to the site in question?

Your theme has a blog description section that’s making the lines and space underneath. Do you have a way to safely edit your theme’s CSS? If so, add the following:

p.lead.blog-description {
    display: none;
}

The image file for your logo has a generous amount of whitespace on the bottom – the easiest fix is probably be to crop it and reload it. Otherwise you’d have to mess with getting other elements to rest on top of it. It’s easy to add space beneath it if you end up cropping it too close for your liking.

For editing CSS (which is what you’re doing), a better practice would be to install a plugin like Jetpack that has a built-in CSS editor, rather than directly adding new CSS to the theme files. Otherwise, if you ever update your theme, you’ll lose your changes.

As it is, when I look at your code, I don’t see the changes you made.