Today I issued and installed SSL certificates for my website.
This is the rating assigned by https://www.ssllabs.com/ssltest/analyze.html :
https://drive.google.com/open?id=1-Fb4h1dmdJ8kN68JxKROWwu4ezGmjm6R
This is the result of https://check-your-website.server-daten.de/ which indicates "only" content problems: mixed, content, missing files, but nothing related to SSL_PROTOCOL
https://drive.google.com/open?id=19i-AwXwgf8tBY9p0srfHX5scN5Q0j-UH

When I connect to the local IP address, everything goes smoothly with no errors:
- after stopping nginx server: https://drive.google.com/open?id=1k4hmYpgRwCW6NyhK7ZoK39-giF9MfPAY
and
- also after restarting nginx server:

(base) marco@pc01:~$ sudo systemctl start nginx
(base) marco@pc01:~$ sudo systemctl reload nginx
(base) marco@pc01:~$ sudo systemctl status nginx
● nginx.service - A high performance web server and a reverse proxy server
Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: en
Active: active (running) since Tue 2020-02-11 19:06:58 CET; 10s ago
Docs: man:nginx(8)
Process: 6124 ExecStop=/sbin/start-stop-daemon --quiet --stop --retry QUIT/5 -
Process: 8843 ExecReload=/usr/sbin/nginx -g daemon on; master_process on; -s r
Process: 8779 ExecStart=/usr/sbin/nginx -g daemon on; master_process on; (code
Process: 8770 ExecStartPre=/usr/sbin/nginx -t -q -g daemon on; master_process
Main PID: 8784 (nginx)
Tasks: 9 (limit: 4915)
CGroup: /system.slice/nginx.service
├─8784 nginx: master process /usr/sbin/nginx -g daemon on; master_pro
├─8844 nginx: worker process
├─8846 nginx: worker process
├─8847 nginx: worker process
├─8849 nginx: worker process
├─8850 nginx: worker process
├─8851 nginx: worker process
├─8852 nginx: worker process
└─8853 nginx: worker process

the output is fine: https://drive.google.com/open?id=1-Sz1udhZfrM9bGaIhImORRnwRznXihK7

But when I connect to my website's through website name I get net::ERR_SSL_PROTOCOL_ERROR :
https://drive.google.com/open?id=10MYySDKhPx9L-QucqzxN5NTratJEOJZR


This is my /etc/nginx/nginx.conf :

user www-data;
worker_processes auto;
pid /run/nginx.pid;
#include /etc/nginx/modules-enabled/*.conf;

events {
worker_connections 768;
# multi_accept on;
}

http {

##
# Basic Settings
##

sendfile on;
tcp_nopush on;
tcp_nodelay on;
keepalive_timeout 65;
types_hash_max_size 2048;
# server_tokens off;

server_names_hash_bucket_size 64;
# server_name_in_redirect off;

include /etc/nginx/mime.types;
default_type application/octet-stream;

##
# SSL Settings
##

#ssl_protocols TLSv1 TLSv1.1 TLSv1.2; # Dropping SSLv3, ref: POODLE
ssl_protocols TLSv1 TLSv1.1 TLSv1.2 TLSv1.3;
ssl_prefer_server_ciphers on;

##
# Logging Settings
##

access_log /var/log/nginx/access.log;
error_log /var/log/nginx/error.log;

##
# Gzip Settings
##

gzip on;
# gzip_vary on;
# gzip_proxied any;
# gzip_comp_level 6;
# gzip_buffers 16 8k;
# gzip_http_version 1.1;
# gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss
text/javascript;

##
# Virtual Host Configs
##

include /etc/nginx/conf.d/*.conf;
#include /etc/nginx/sites-enabled/*;
}


And this is my /etc/nginx/conf.d/default.conf :

server {
listen 443 ssl http2 default_server;
server_name ggc.world;

ssl_certificate /etc/letsencrypt/live/ggc.world/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/ggc.world/privkey.pem; # managed by Certbot

ssl_trusted_certificate /etc/letsencrypt/live/ggc.world/chain.pem;

ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot

ssl_session_timeout 5m;
#ssl_protocols TLSv1 TLSv1.1 TLSv1.2 TLSv1.3;
ssl_protocols TLSv1.2 TLSv1.3;
ssl_ciphers EECDH+CHACHA20:EECDH+CHACHA20-
draft:EECDH+AES128:RSA+AES128:EECDH+AES256:RSA+AES256:EECDH+3DES:RSA+3DES:!MD5;
ssl_prefer_server_ciphers on;
ssl_session_cache shared:SSL:50m;
ssl_stapling on;
ssl_stapling_verify on;

access_log /var/log/nginx/ggcworld-access.log combined;

add_header Strict-Transport-Security "max-age=31536000";
location = /favicon.ico { access_log off; log_not_found off; }

location / {
proxy_pass http://127.0.0.1:8080;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
}
}

server {
listen 80 default_server;
listen [::]:80 default_server;
error_page 497 https://$host:$server_port$request_uri;
server_name www.ggc.world;
return 301 https://$server_name$request_uri;

access_log /var/log/nginx/ggcworld-access.log combined;

add_header Strict-Transport-Security "max-age=31536000";
location = /favicon.ico { access_log off; log_not_found off; }

location / {
proxy_pass http://127.0.0.1:8080;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
}
}

upstream websocket {
ip_hash;
server localhost:3000;
}

server {
listen 81;
server_name ggc.world www.ggc.world;

#location / {
location ~ ^/(websocket|websocket\/socket-io) {
proxy_pass http://127.0.0.1:4201;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
proxy_set_header X-Forwared-For $remote_addr;
proxy_set_header Host $host;

proxy_redirect off;
proxy_set_header X-Real-IP $remote_addr;
}
}


What is going on? What might be the causes of this SSL_PROTOCOL?
How to solve it? What do I have to modify in /etc/nginx/conf.d/default.conf?

Looking forward to your kind help.
Marco