Hi,

Users with avatar and their own custom fileds.

Yes, you can try free version to see avatar and custom fields (only text field type is available in free version)

Users can send a messages to eachother

This is possible with Social Network Plugin (included in Pro version), check demo site to check if this met your needs (http://socialnetwork.easy-profile.com/)

Users can have own gallery (images and maybe videos)

This is possible with Social Network Plugin (included in Pro version), check demo site to check if this met your needs (http://socialnetwork.easy-profile.com/). In social network plugin you can share videos from youtube or vimeo, you can't upload video files.

Users can post a comments under my articles or other users gallery, profile (not by facebook)

We not provide any comment plugins for articles, anyway in Social Network plugin we provide a simple blog, here is possible to add comments.

Searching users by custom fileds

Yes, this is possible

Multilangue

In Easy Profile included following languages: English, German and Italian. If you need other languages you need to translate (the way to translate is the same of all Joomla component)
Social Connect plugin included following languages: English, Italian and Portuguese. You translate plugin by follow docs at http://docs.easy-profile.com/index.php/article/social-network-make-your-language.

But how about translation for Custom Fields ?
On your demo site i see GENDER BIRTHDAY (even in Italian)

ps: where can i add more images to my gallery (beside cover)?

But how about translation for Custom Fields ?

see docs at http://docs.easy-profile.com/index.php/article/translate-fields

ps: where can i add more images to my gallery (beside cover)?

Sorry, Where?

Is there any chance ?

Yes and No, You can create a simple page and embed your video (if your video extensions allow this)

see this example http://socialnetwork.easy-profile.com/pages/video , I have embed a youtube video.

so your "simple page" is a typical joomla article (with tiny mce etc?)

No, this is a page from our Social Network Plugin, see screenshot