Nginx Stopped Working after installing Let's Encrypt on Ubuntu 20.04

I tried to install Let’s Encrypt on my Ubuntu 20.04 by following this article: https://www.digitalocean.com/community/tutorials/how-to-secure-nginx-with-let-s-encrypt-on-ubuntu-20-04#step-4-%E2%80%94-obtaining-an-ssl-certificate and after installing Nginx stopped working and I can’t start Nginx anymore.

These are a few of the tests:

#sudo vim /etc/nginx/sites-enabled/mydomain
server {

  server_name domain.com www.domain.com;

#sudo nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful

#sudo systemctl start nginx
Job for nginx.service failed because the control process exited with error code.
See "systemctl status nginx.service" and "journalctl -xe" for details.

#sudo ufw status
Status: inactive

and certbot asked me: Please choose whether or not to redirect HTTP traffic to HTTPS, removing HTTP access. I selected to redirect. And when I visit my site without https I get 502 Bad Gateway and when I go with https I get domain.com refused to connect.

Any help is appreciated and thanks in advance