In your screenshot, you have database host : Localhost. You should change it to your postgresql host, i believe the 35.200.156.83
Also i don't know if your OS is equiped with SELinux, but it could be that you need to alter the SElinux config to allow http and php to communicatie to your database. For mysql you need the following selinux configs :
setsebool -P httpd_can_network_connect 1
setsebool -P httpd_can_network_connect_db 1