Problems when playing in multiplayer.

you need to put Hamachi at the top of the list, I did it, my friend hasn't tried it yet

That's what I wrote. But it needs to be set up for both.

and my antivirus is Avira, I don't know what my friend's is

Look through the settings, turn off network firewalls, etc. if there are any. And you can also temporarily turn off the antivirus altogether. ;)

in the Start menu, the Nival interactive section doesn't seem to be related to 1C or Buka

Either 1C or Buka - there's no other option if it's the Russian version. ;)
You can check this: in the main menu of the game, at the top left, if the inscription "Tribes of the East" is in English, then it's 1C, if it's in Russian "Tribes of the East", then it's Buka.