That requires a skill set to modify a file that has all the information related to modification
Most Probably under normal cases resides below
/etc/apache2/sites-available/000-default-le-ssl.conf
The SSL needs to be renewed like below ( requires certbot to be installed )
sudo certbot --apache -d gatoon.org -d www.gatoon.org
The entire virtual hosts file looks like
ServerAdmin webmaster@localhost DocumentRoot /var/www/html ErrorLog ${APACHE_LOG_DIR}/error.log CustomLog ${APACHE_LOG_DIR}/access.log combined ServerName gatoon.com Include /etc/letsencrypt/options-ssl-apache.conf ServerAlias www.gatoon.com SSLCertificateFile /etc/letsencrypt/live/gatoon.com/fullchain.pem SSLCertificateKeyFile /etc/letsencrypt/live/gatoon.com/privkey.pem ServerAdmin webmaster@localhost DocumentRoot /var/www/html ErrorLog ${APACHE_LOG_DIR}/error.log CustomLog ${APACHE_LOG_DIR}/access.log combined ServerName gatoon.net Include /etc/letsencrypt/options-ssl-apache.conf ServerAlias www.gatoon.net SSLCertificateFile /etc/letsencrypt/live/gatoon.net/fullchain.pem SSLCertificateKeyFile /etc/letsencrypt/live/gatoon.net/privkey.pem ServerAdmin webmaster@localhost DocumentRoot /var/www/html ErrorLog ${APACHE_LOG_DIR}/error.log CustomLog ${APACHE_LOG_DIR}/access.log combined ServerName gatoon.org Include /etc/letsencrypt/options-ssl-apache.conf ServerAlias www.gatoon.org SSLCertificateFile /etc/letsencrypt/live/gatoon.org/fullchain.pem SSLCertificateKeyFile /etc/letsencrypt/live/gatoon.org/privkey.pem