Hi there,
Firstly please use the plugin Font Awesome Shortcodes, if this also didn’t help you then please provide us your login details (WP-login details) via mail so it will be easy for both of us to find the solution of the problem.
Note: Please take a backup of your site before proceeding. Normally we use duplicator plugin to make a backup. https://wordpress.org/plugins/duplicator/.
Here is the video tutorials how to use duplicator and save it to your local computer https://www.youtube.com/watch?v=VdvOGV2eIjE
Please use this Email Address: [email protected] to send your WP-login details.
Thanks.