ah!
tail -f /var/log/nginx/error.log
[error] 743#743: *472 no "ssl_certificate" is defined in server listening on SSL port while SSL handshaking, client: 93.8.74.91, server: 0.0.0.0:443
as for iptables rules
-A ufw-user-input -p tcp -m tcp --dport 80 -j ACCEPT
-A ufw-user-input -p tcp -m tcp --dport 443 -j ACCEPT
edit : OK I fixed it by adding "default_server" in my server block conf.
listen 443 default_server ssl http2;
PS : gonna add this AAAA record 
Thank you very much for your time
enjoy your sunday 