There are a lot of ways to add “sections” to a page. You question is really very broad. I’ll try to give you some idea but you will have to research most of them here and on the Codex as I don’t have time to write code for each option.
- Widgets. One of the simplest ways to create sections of content
is with widgets. You can identify where the widgets should show up
via code in the page template and then fill the space by placing
widgets in the backend via the “Appearance->Widgets” panel. - Post content. Your page has a block of content built in already.
Just create a Loop to display it. - Custom meta fields. Your page should already have meta field
capabilities. Use it. - Multiple Loops. You don’t have to use just one Loop for content. You
can create multiple secondary Loops. - Child pages. Use child pages to pull extra content into the
page via a secondary Loop. - Dedicated post type. Like the child page option above but using
a custom post type. Something like this:
https://wordpress.stackexchange.com/a/211911/21376 - Options. This is very similar to what you are doing already but
you would need to write all of the code, including the backend form. - Theme customizer. You can also add similar options via the
theme customizer.