Plesk 12.x / Linux :: PHP Files Get Downloaded With Fast-CGI

I'm trying to get something simple to work in Plesk. I just want to use Apache for PHP files with Fast-CGI and PHP 5.6. Everything works fine with Nginx and PHP-FPM but because of the restrictions, that Nginx can only use a systemwide PHP version, which is 5.3.3 in my case, I need Apache for that.

So the problem is that I get the .php files as download and Apache doesn't parse them.

A little background information:
Cent OS 6.6
Plesk 12.0.18 Update #49
PHP Versions 5.3.3 and 5.6.9
PHP Handles installed with this KB [URL] ....:

Code:
id: display name: full version: version: type: cgi-bin: php-cli: php.ini: custom:
cgi 5.3.3 5.3.3 5.3 cgi /usr/bin/php-cgi /etc/php.ini false
fastcgi 5.3.3 5.3.3 5.3 fastcgi /usr/bin/php-cgi /etc/php.ini false
module 5.3.3 5.3.3 5.3 module /usr/bin/php-cgi /etc/php.ini false

[Code] ....

Hosting templates are default and I checked every configuration file...