But, germany begin creating a lot of offensive units, while URSS make a lot of infantry first, and then a couple of IS2, lengthening his offensive phase until Germany take the initiative. I wish i could make Russia to begin attacking early
Given that this is a scenario with preplaced towns (and units?), I have a couple of questions:
(1) Is the (Russian) Infantry unit flagged as a "Defensive" unit (under AI-strategy)?
(2) Do the Russians also start with a lot of their towns minimally- or undefended?
If yes to both questions, then that is likely why the Russions are slow(er) to start fighting.
The AI 'needs' to ensure that its towns are adequately defended (at least 2 defenders even in a Size-1 town, +1 defender for each size-increase, and — I think — also per Wonder),
before it will start building 'Offensive'-flagged units from that town. And for any town which does not meet that standard, the AI will build any 'needed' defenders
in situ. It also does not generally move defenders out of the towns where they were built, unless escorting a Settler, or going on pillaging-missions (but it will only do the latter if it has built 'excess' defenders).
So if you want Russia to start building attackers from the start, you may need to preplace (more) town-defenders?