Gitlab site says to configure Gitlab-CE installation, what can I do get back into my site?

That is quite alright.

If you would like to give it a shot. (backup your Gitlab configuration file)

This is how I run my Gitlab installation - non-bundled NGINX webserver

http://www.creativespacesbysherihannah.com/wp-sys/wp-content/uploads/staircase-before.jpg?TB_iframe=true&width=700&height=351

You will need to install NGINX

wget https://nginx.org/keys/nginx_signing.key -O - | sudo apt-key add -

echo "deb http://nginx.org/packages/mainline/ubuntu/ xenial nginx deb-src http://nginx.org/packages/mainline/ubuntu/ xenial nginx" > /etc/apt/sources.list.d/nginx.list

apt-get -y update

apt-get -y install nginx

this will install NGINX Mainline

My NGINX configuration looks like this - replace YOUR_SERVER_FQN with your server domain

upstream gitlab-workhorse {
  server unix:/var/opt/gitlab/gitlab-workhorse/socket fail_timeout=0;
}


server {

  listen 0.0.0.0:80;

  server_name YOUR_SERVER_FQN;
  server_tokens off;
  
  location / {
    return 301 https://$http_host$request_uri;    
  }
  
  # Letsencrypt Verification
  #
  location ~ /.well-known {
    root /usr/share/nginx/html;
    allow all;
  } 

  access_log  /var/log/nginx/gitlab_access.log;
  error_log   /var/log/nginx/gitlab_error.log;

}


server {

  listen 0.0.0.0:443 ssl;

  server_name YOUR_SERVER_FQDN;
  server_tokens off;

  root /opt/gitlab/embedded/service/gitlab-rails/public; 

  ssl on;
  ssl_certificate /etc/letsencrypt/live/git.YOUR_SERVER_FQN/fullchain.pem;
  ssl_certificate_key /etc/letsencrypt/live/git.YOUR_SERVER_FQN/privkey.pem;
  
  ssl_protocols TLSv1 TLSv1.1 TLSv1.2;

  ssl_prefer_server_ciphers on;
  ssl_ciphers "ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES128-SHA:ECDHE-RSA-DES-CBC3-SHA:AES256-GCM-SHA384:AES128-GCM-SHA256:AES256-SHA256:AES128-SHA256:AES256-SHA:AES128-SHA:DES-CBC3-SHA:!aNULL:!eNULL:!EXPORT:!DES:!MD5:!PSK:!RC4";
  ssl_ecdh_curve secp384r1;

  ssl_session_cache shared:SSL:10m;
  ssl_session_tickets off;

  ssl_stapling on;
  ssl_stapling_verify on;

  resolver 8.8.8.8 8.8.4.4 valid=300s;
  resolver_timeout 5s;
  
  add_header Strict-Transport-Security "max-age=63072000; includeSubdomains";
  add_header X-Frame-Options DENY;
  add_header X-Content-Type-Options nosniff;
  
  ssl_dhparam /etc/ssl/certs/dhparam.pem;  
  
  access_log  /var/log/nginx/gitlab_access.log;
  error_log   /var/log/nginx/gitlab_error.log;

  location / {
    client_max_body_size 0;
    gzip off;

    proxy_read_timeout      300;
    proxy_connect_timeout   300;
    proxy_redirect          off;

    proxy_http_version 1.1;

    proxy_set_header    Host                $http_host;
    proxy_set_header    X-Real-IP           $remote_addr;
    proxy_set_header    X-Forwarded-Ssl     on;
    proxy_set_header    X-Forwarded-For     $proxy_add_x_forwarded_for;
    proxy_set_header    X-Forwarded-Proto   $scheme;
    proxy_pass http://gitlab-workhorse;
  }

}

I have the same problem, But still can’t fix it. Are there any idea. Please help us. :(

Take a look at https://docs.gitlab.com/omnibus/settings/nginx.html#inserting-custom-nginx-settings-into-the-gitlab-server-block - add this to the server block

location ^~ /.well-known/acme-challenge/ {
  default_type "type/plain";
  root /tmp/letsencrypt;
}

issue this command mkdir /tmp/letsencrypt

Restart Gitlab and then try and renew the SSL

… or you can reconfigure gitlab to not use SSL