Help…PHP for social plugin has crashed my site…!

Site and all access has crashed after trying to install php code for floating social media icons.

Have followed these steps with no avail…
1. Via FTP, find the wp-config.php file (root directory), and locate this line:
define(‘WP_DEBUG’, false);

Change the ‘false’ to ‘true’ – then reload the page in your browser. – Same 500 server error.

2. Went through my browsing history and located the first “error” page (https://www.breanek.net/BREANEKnew/wp-admin/theme-editor.php?file=functions.php&theme=headway&scrollto=0&updated=true.) and have gone in via FTP to “wp-admin/theme-editor.php” copied the PHP code and run a code check through various online tools and come back with two results…
a – (is the most common) Parse error: syntax error, unexpected T_OBJECT_OPERATOR in CODE on line 23 Errors parsing CODE…
Line 23: get_current_screen()->add_help_tab( array(

or

b – Error: There is 1 array declaration that contain a single equal sign ‘=’ instead of ‘=>’:
Error: There are 3 array declarations that contain text character variables or values without quotations:

I’m a relative novice to this, I built the site quite happily using Headway Themes and have changed a small amount of HTML & CSS as I’ve learnt about it with positive results. I was following the video tutorial for the social media icon plugin and hit ‘update’ only for the site to crash and now I can’t access ANYTHING other than https://FTP…HELP?!?!