Prepare ssl-params

openssl dhparam -out /etc/ssl/certs/dhparam.pem 2048

vim /etc/nginx/snippets/ssl-params.conf

ssl-params.conf, from: https://syslink.pl/cipherlist/, modify ssl_dhparam, resolver

ssl_protocols TLSv1.3;# Requires nginx >= 1.13.0 else use TLSv1.2
ssl_prefer_server_ciphers on;
# ssl_dhparam /etc/nginx/dhparam.pem; # openssl dhparam -out /etc/nginx/dhparam.pem 4096
ssl_ciphers EECDH+AESGCM:EDH+AESGCM;
ssl_ecdh_curve secp384r1; # Requires nginx >= 1.1.0
ssl_session_timeout  10m;
ssl_session_cache shared:SSL:10m;
ssl_session_tickets off; # Requires nginx >= 1.5.9
ssl_stapling on; # Requires nginx >= 1.3.7
ssl_stapling_verify on; # Requires nginx => 1.3.7
# resolver 1.1.1.1 1.0.0.1 [2606:4700:4700::1111] [2606:4700:4700::1001] valid=300s; # Cloudflare
resolver 1.1.1.1 1.0.0.1 valid=300s; # Cloudflare
resolver_timeout 5s;
add_header Strict-Transport-Security "max-age=63072000; includeSubDomains; preload";
add_header X-Frame-Options DENY;
add_header X-Content-Type-Options nosniff;
add_header X-XSS-Protection "1; mode=block";

# Paste this at the bottom of the file
ssl_dhparam /etc/ssl/certs/dhparam.pem;

Configure the server

vim /etc/nginx/sites-enabled/your.domain.conf

server {
    listen 443 ssl http2; # HTTP2 requires nginx >= 1.9.5
    # listen [::]:443 ssl http2;
    server_name example.com; # REPLACE HERE

    ssl_certificate /etc/nginx/ssl/xxx.domain/fullchain.pem; # REPLACE HERE
    ssl_certificate_key /etc/nginx/ssl/xxx.domain/privkey.pem; # REPLACE HERE

    include snippets/ssl-params.conf;

    location / {
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-NginX-Proxy true;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection 'upgrade';
        # REPLACE HERE
        proxy_pass http://localhost:5000/;
        proxy_ssl_session_reuse off;
        proxy_set_header Host $http_host;
        proxy_pass_header Server;
        proxy_cache_bypass $http_upgrade;
        proxy_redirect off;
    }
}

Test

nginx -t
nginx -s reload

curl -v --http2 https://your.domain