how to install ssl on server

I followed all the things given in link
https://www.linode.com/docs/security/ssl/ssl-apache2-debian-ubuntu/
but still am facing error while apache2 service restart or reload
service apache2 restart
Job for apache2.service failed because the control process exited with error code.
See "systemctl status apache2.service" and "journalctl -xe" for details.

I have multiple .conf file for subdomains. I am adding ssl data in my main website .conf file.

my site .conf file

<directory "="" var="" www"=""> Require all granted AllowOverride None </directory>

<directory "="" advanced="" consumer="" example.com="" html="" var="" web"="" www=""> AllowOverride All </directory>

<virtualhost *:80="">
ServerName example.com
ServerAlias www.example.com
ServerAdmin admin@example.com
DocumentRoot "/var/www/html/example.com/advanced/consumer/web/"</virtualhost>

ErrorLog /var/www/html/example.com/logs/error.log
CustomLog /var/www/html/example.com/logs/access.log combined

<directory "="" advanced="" consumer="" example.com="" html="" var="" web="" www=""></directory>

<virtualhost *:443="">
SSLEngine On
SSLCertificateKeyFile /var/www/html/example.com/ssl/STAR.example.com/STAR.example.com.key
SSLCertificateFile /var/www/html/example.com/ssl/STAR.example.com/STAR.example.com.crt
SSLCertificateChainFile /var/www/html/example.com/ssl/STAR.example.com/STAR.example.com.ca-bundle</virtualhost>

ServerName example.com
ServerAlias www.example.com
ServerAdmin admin@example.com
DocumentRoot "/var/www/html/example.com/advanced/consumer/web/"

ErrorLog /var/www/html/example.com/logs/error.log
CustomLog /var/www/html/example.com/logs/access.log combined

<directory "="" advanced="" consumer="" example.com="" html="" var="" web="" www=""></directory>