help me understand NGINX

[drew571]

Sorry but I'm new to NGINX and i have a few questions.  Please bear with me.
 My understanding of NGINX is that it allows me to just keep port 443 open
and NGINX will forward the traffic to the correct IP address and port inside
my network based on the domain being used to get to my NGINX instance.  Do I
have that right?  

Right now I have NGINX set to forward a duckdns domain to my Home Assistant
instance.  The NGINX is actually installed on my home assistant as an addon.
 

I also have another domain that is a synology.me domain that I setup on my
synology server that forwards that domain to my synology logon screen. 
NGINX is getting me to the login screen but I am getting the message that it
is not secure.  How would I go about fixing this?  

Likewise I would like to setup another domain name that would get me to my
router login.  Obviously I know what ip and port my router is and i setup an
addition domain with duckdns.  I just keep getting internal errors when I
hit save on my new proxy host in NGINX.

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,292066,292066#msg-292066