David_G

Try this:

/*
Theme Name:     OneEngine Child
Theme URI:      http://www.startupweb/themes/oneengine-child
Description:    a free WordPress one-page theme, built with simplicity in mind and optimized for better user interactions
Author:         EngineThemes Team
Author URI:     http://www.enginethemes.com
Template:       oneengine
Version:        1.1
*/
/* Your customizations start here */

And this for your functions:

<?php

?>

Good, I see you got your site back online. Here is what you need to create a child-theme. This will also make it easier to fix a mistake. It is not wise to edit the core WP or Theme files.

The best way to make changes like this to a theme is to use a child theme, so your tweaks won’t be overwritten when updating the theme. Here are some guides in case you haven’t made one before:
https://codex.wordpress.org/Child_Themes
http://op111.net/53/

Coding, place this in your style.css, preferably in a child-theme or custom css.

.post_meta ul li {
  display: none;
  }

OK, suggest you download a fresh copy of your theme, and extract it on your computer.
Once you get to your ftp going, you need to change your functions.php file to functions.old. You will find that in your

WP-CONTENT / THEMES / YOUR-THEME / functions.php

Then upload the functions.php file from the files you downloaded and extracted.

For FTP, the ip address to your site should be: 173.254.28.114
Then enter your hosting username & PW.

Ask your host for FTP details also.

Normally editing css wont crash the site, functions.php mistakes will crash it. Is your site on a cpanel host?

The button links should be in your setup.