Looks OK to me: See https://i.imgur.com/HWrWL7i.png

Where are you seeing them missing?
use this.
1. for scroll to top
<i class="fa fa-angle-up"></i>
2. for user icon
<i class="fa fa-user"></i>
thanks
The to-top is incorrectly coded as “fas fas-long-arrow-alt-up”. See https://i.imgur.com/KYb2jF1.png

There is a search icon in the nav, an up arrow at the bottom and the previous/next arrows aren’t showing.
This theme has about 50 different php and css files in it, and (sorry I’m mediocre when it comes to dev stuff) I can’t figure out where the heck it needs to change.
This is how FA is added to your site:
<link rel='stylesheet' id='font-awesome-css' href='https://christineschulzwrites.com/wp-content/plugins/elementor/assets/lib/font-awesome/css/font-awesome.min.css?ver=4.7.0' type='text/css' media='all' />
Based on that URL, I recommend asking at https://wordpress.org/support/plugin/elementor/#new-post so the plugin’s developers and support community can help you with this.
I will try asking. I contacted the theme developers with no success. I understand HTML and CSS pretty well, and how to use the Theme Editor. However, I’m a little new with WordPress. I can copy and paste that code, I just don’t know which file I need to paste it into.
Actually, I just downloaded the fontawesome plugin and it seemed to fix it. I’m still not sure what went missing where, but the plugin appears to be a good work around.