So, is it possible to change % of resists for each difficulty, for ex. -20% to all on normal difficulty?
You are an evil person, if you can do that. 
Well, yep, thats me:p But i still cant find any entities about difficulty in database.arz…
Maybe it is in the map definition?
Maybe it is part of the core of the game, and cannot be modified
Here you go:
records/game/balancingadjustment_mp+difficulty_players01.dbr
It’s a file that is linked in records/game/gameengine.dbr as balancingadjustment for difficulties.
The values are always pairs of 4 as there can 4 players join online so you need to modify the first 4 values in the array for normal difficulty, the following for elite and the last 4 for ultimate
oh god, thanks to you so much!