More than half. The vast majority of Soviet population and industrial base was in the burned-down part.

Who supported Russia after the war?

The conquered countries that were stripped of a good part of what they had, largely.

would appreciate a reference.

p.s. many parts of eastern europe has been destroyed during the war as well; and was getting rebuild themselves.

Most of what was left of factories in the Soviet occupation zone (the later GDR) was dismantled and moved to the Soviet Union as reparation in the years after WW2. Here's some info in English about this: https://en.wikipedia.org/wiki/Economy_of_the_German_Democrat...

When I was young I heard a lot of crazy stories about the Russians in Germans (I grew up in the Erzgebirge mountains where the Russians mined the Uranium for their atomic bombs, think of an Eastern 20th century gold rush), some of those stories are how entire production lines were moved onto trains and to the Soviet Union nearly over night (they had a lot of experience with this since a few years earlier the Soviet Union basically moved their entire military production a few thousand kilometers eastward, out of the war zone).

Interesting, thanks.

Here's a reference for you https://en.wikipedia.org/wiki/Gulag People all across occupied lands were enslaved (on paper sentenced for some nonsense and send to workjails)

I was referring to the massive lend-lease support, and the continued industrial support provided to the Soviet Union during the war, not after war. I should have been more clear about that.