Use Varnish & NGINX to Serve WordPress over SSL & HTTP on Debian 8

Update the guide with the observations and suggestions:

If you get "Too many redirects" error as I was getting, this will fix it:

Open wp-config.php in your root wordpress directory
Add this line to the end of the file:

$_SERVER['HTTPS']='on';

PS: I'm still going through 1 more issue of some of the content loading like my header and slider, working on it. I don't think javascript is working. This is on Ubuntu 18.04.3 LTS (Bionic Beaver), nginx/1.14.0, varnish-5.2.1, php7.2

EDIT: Correction, add that line to the beginning of the wp-config.php file, along with these lines:
define('FORCE_SSL', true);
define('FORCE_SSL_ADMIN',true);
$_SERVER['HTTPS']='on';

If you have a problem with some content not loading as I did it's most likely because your site is trying to send javascript and cascade style sheets over http instead of https. I initiated a plugin called "http-https-remover" which solved this. Everything working 100% now thanks!
****************************************************************************************************Varnish was crashing after start and I couldn't figure out why...

I had to add a -F flag:
ExecStart=/usr/sbin/varnishd -F -a :80 -T localhost:6082 -f /etc/varnish/custom.vcl -S /etc/varnish/secret -s malloc,1G

After editing /lib/systemd/system/varnish.service i had to daemon-reload and tried starting varnish again and it worked. I was told if varnish.service was modified that a -F flag is required and it happened to fix my problem.

Start with the guide titled “Use Varnish & NGINX to Serve WordPress over SSL & HTTP on Debian 8” and compare its instructions with the reported setup details. Review the references to wp-config.php, /lib/systemd/system/varnish.service, and /etc/varnish/custom.vcl; done means incorporating only verified, still-relevant guidance about redirects, mixed content, and the Varnish service.