It seems the bnsupport tool did not catch some of the files we were looking for. Could you show us the contents of the following file?
In any case, there seems to be an issue with your web application. For example you could try to install the Bitnami WordPress module, and you will see it works perfectly without any gateway timeout issues.
Have you developed your web application in local? If so, does it work correctly there? We recommend you to check if it performs long-running operations, a high number of database or file requests, as it could be related.
You could always look into disabling PHP-FPM. In order to do that, edit /opt/bitnami/apache2/conf/httpd.conf and change the following lines:
LoadModule mpm_event_module modules/mod_mpm_event.so
#LoadModule mpm_prefork_module modules/mod_mpm_prefork.so
#LoadModule php7_module modules/libphp7.so
#LoadModule mpm_event_module modules/mod_mpm_event.so
LoadModule mpm_prefork_module modules/mod_mpm_prefork.so
LoadModule php7_module modules/libphp7.so
Then stop PHP-FPM and restart Apache:
sudo /opt/bitnami/ctlscript.sh stop php-fpm
sudo /opt/bitnami/ctlscript.sh restart apache
If it works correctly now, you can disable PHP-FPM with the following command:
sudo mv /opt/bitnami/php/scripts/ctl.sh /opt/bitnami/php/scripts/ctl.sh.disabled