Warning: session_start(): Cannot send session cookie – headers already sent by

I recently attempted to add multisite to my WordPress site and got stuck with the following warning:

Warning: session_start(): Cannot send session cookie – headers already sent by (output started at /usr/www/users/useacfhvse/wp-config.php:1) in /usr/www/users/useacfhvse/wp-content/themes/DL/framework/_config.php on line 72 Warning: session_start(): Cannot send session cache limiter – headers already sent (output started at /usr/www/users/useacfhvse/wp-config.php:1) in /usr/www/users/useacfhvse/wp-content/themes/DL/framework/_config.php on line 72 Warning: Cannot modify header information – headers already sent by (output started at /usr/www/users/useacfhvse/wp-config.php:1) in /usr/www/users/useacfhvse/wp-includes/pluggable.php on line 918 Warning: Cannot modify header information – headers already sent by (output started at /usr/www/users/useacfhvse/wp-config.php:1) in /usr/www/users/useacfhvse/wp-includes/pluggable.php on line 919 Warning: Cannot modify header information – headers already sent by (output started at /usr/www/users/useacfhvse/wp-config.php:1) in /usr/www/users/useacfhvse/wp-includes/pluggable.php on line 920 Warning: Cannot modify header information – headers already sent by (output started at /usr/www/users/useacfhvse/wp-config.php:1) in /usr/www/users/useacfhvse/wp-content/themes/DL/framework/class/class_core.php on line 5896

I altered the wp-config.php and .htaccess files without making backups and now I cannot log-in to the systems any more. I use the responsive Car Dealer Theme.
http://www.useacar.co.za
Any suggestions?