Seriously though, all of these russophobic eastern european countries are like: "Russia took our lands".
First of all, it was not Russia but USSR who took your lands; second, USSR did not give these lands to Russia (even in the form of RSFSR) but to other russophobic eastern european countries.
You are grown-ups now. Sort it out between yourselves.
Russia is officially the successor state of the USSR. So legally yes, the USSR is Russia in so far as anyone cares for the purposes of assigning blame.
I don't really want to get involved in this argument, but I think this is a situation where there's just a little bit of missing historical background that might help you two understand one another. What the upstream commenter is referring to is the fact that the land that was historically eastern Poland isn't part of Russia now -- it's part of Ukraine and Belarus. Sure, the USSR (of which Russia is the successor state) is what performed that land transfer, but the land was not transferred to what is now Russia.
> the land that was historically eastern Poland isn't part of Russia now -- it's part of Ukraine and Belarus
The Belarussian / Polish border today is almost exactly the border between Kingdom of Poland and Grand Duchy of Lithuania within the Polish–Lithuanian Commonwealth. So "historically eastern Poland" is not right there. Some like to think of the whole Commonwelth as Poland, which really dominated there. But in this case whole Belarus and Ukraine are "eastern Poland".
That's what poles tried to restore when got chance to recreate their state after WWI, as I understand. The full commonwealth. But only got to the borders we know as the pre-1939 Poland.
BTW, Ukraine is mostly the part of the GDL annexed by the Kingdom of Poland during the Union of Lublin. The todays Belarus / Ukraine border goes by this line.
They (USSR was Russian-lead) were literally allied with Nazi-Germany and agreed to split Europe with them. They executed 20000+ Polish people in Katyn alone.
USSR was actually much worse than Nazi Germany. They had much more time to do bad things.
And even if we only account WWII timeline, people in territories between Germany and USSR preferred to be conquered by Germans, purely because their soldiers were more disciplined than the ones from USSR (which were just peasants, frequently even without boots, equipped with weapons).