Regarding Poland, again, this was territory Poland had conquered previously that historically belonged to countries in the Soviet Union. This was a return of territory. By no means did it come without bloodshed, but nevertheless the soviets were not nearly the butchers the Nazis were.

As for the west conspiring to kill of the Soviet Union, and letting Germany do so, again, I gave naked testimony that this was the case. The Soviet Union wanted above all else to survive, the Nazis wanted new colonial territories, and the west wanted to not get colonized by the Nazis while also wanting the Soviets to stop being socialist.

Do you have a source on a British warning to Germany?

Wolkow W. K. (2003), Stalin wollte ein anderes Europa. Moskaus Außenpolitik 1940 bis 1968 und die Folgen, Edition Ost, Berlin, p. 110.

The British warnings to the USSR were sadly ignored; Stalin did not order the Red Army to get ready for an invasion, which was partially why the first few months of the war went so disastrously poorly for the Soviets.

I already explained this earlier. There was a massivedisinformation campaign, with feints from both Germany and the western powers. The first few weeks went as everyone expected, the Nazis advanced quickly over largely open land until running face to face with the full industrialized might of the Red Army. Goebbels' diary is quite telling of the change in attitude. On the 22nd-23rd of June, the Nazis attacked confidently. On July 2nd, Goebbels wrote the following:

Overall, the fighting is hard and stubborn. We can in no way speak of a walk in the park. The red regime has mobilized the people.

July 24th:

We can have no doubt whatsoever about the fact that the Bolshevik regime, which has existed for nearly a quarter of a century, has left a deep mark on the peoples of the Soviet Union […]. It would be right, therefore, if we clearly informed the German people about the harshness of the struggle taking place in the East. The nation must be told that this operation is very difficult, but that we can and will survive it.

August 1st:

At the Führer’s headquarters […] they also openly admit that they were somewhat mistaken in their assessment of Soviet fighting power. The Bolsheviks are showing stronger resistance than we expected, and above all the material means at their disposal are greater than we had anticipated.

August 9th:

Privately, the Führer is very displeased for having allowed himself to be so deceived about the potential of the Bolsheviks by the reports [sent by German agents] coming from the Soviet Union. In particular, the underestimation of the enemy’s tanks and aircraft caused a great deal of trouble for our military operations. He suffers a lot because of this. We’re dealing with a serious crisis […]. The previous campaigns were a walk in the park by comparison […]. The Führer is not worried about the West […]. In our German thoroughness and objectivity we have always overestimated the enemy, except, in this case, the Bolsheviks.

September 16th:

We have totally underestimated the strength of the Bolsheviks.

This was not a walk in the park for the Nazis, because the Soviets planned for it. Modern historiography makes it quite clear that the Nazis and Soviets were never allies in any capacity, for any length of time, and were always conspiring against each other with no expectation of actual peace, just biding their time before what they desired to be a favorable start to war.