CMS, of course, needs to be integrated with the forum.
Ideally you need the ability to create custom post formats - for example, to generate a post template from the downloaded file, two images and text.
Still need the ability to switch interface between Russian - and English-speaking.
Now put the WordPress + Wp_united, finished wordpress to the desired functionality, but it is not very like.
The rest - easier than this CMS will be better.