1 - install nginx
sudo apt update
sudo apt install nginx -y
sudo systemctl enable nginx
sudo systemctl start nginx
sudo systemctl status nginx
sudo ufw allow 'Nginx Full'
sudo ufw status
sudo ufw allow 22/tcp
sudo ufw allow 80/tcp
sudo ufw allow 443/tcp
sudo ufw enable
sudo ufw status

2 - SSL Setup
sudo systemctl restart nginx
sudo nginx -t
sudo systemctl reload nginx
sudo apt update
sudo apt install certbot python3-certbot-nginx -y
sudo ufw allow 'Nginx Full'
sudo certbot --nginx -d yourdomain.com -d www.yourdomain.com
sudo certbot renew --dry-run

3 - Subdomains
sudo nano /etc/nginx/sites-available/test1.yourdomain.com
sudo nano /etc/nginx/sites-available/test2.yourdomain.com
sudo mkdir -p /var/www/test1 /var/www/test2
echo "<h1>Test1 Subdomain</h1>" | sudo tee /var/www/test1/index.html
echo "<h1>Test2 Subdomain</h1>" | sudo tee /var/www/test2/index.html
sudo ln -s /etc/nginx/sites-available/test1.yourdomain.com /etc/nginx/sites-enabled/
sudo ln -s /etc/nginx/sites-available/test2.yourdomain.com /etc/nginx/sites-enabled/
sudo nginx -t && sudo systemctl reload nginx

4 - SSL in Subdomains
sudo certbot --nginx -d test1.yourdomain.com
sudo certbot --nginx -d test2.yourdomain.com
sudo certbot renew --dry-run