I have seen , there are no manual for this game . Do you think , gog can obtain one for the downloading ?

I think game creators working on it. Manual should be translated from Russian. I'm happy that they translate the game and we can play in English :)

There is fantastic tutorial at the start of the campaign - it helps a lot.

Also in this thread you can find some useful files:
http://www.gog.com/forum/eador_genesis/about_better_units_and_fort

Take a look here it really helped me a lot :)
http://translate.google.com/translate?act=url&depth=1&hl=en&ie=UTF8&prev=_t&rurl=translate.google.com&sl=ru&tl=en&u=http://eador.com/en/page3.html

This topic should be made a sticky