At the time of the February revolution Lenin (and many other would be Russian revolutionaries) was in Switzerland. Imperial Germany agreed to take Lenin (and others) to Russian in a sealed train. The Germans did this because they were trying to undermine Russia's ability to participate in the Great War. The German Empire didn't want to promote Proletarian Internationalism. After this there is no evidence of further cooperation, and while there was some White propaganda during the Civil War that alleged that Lenin was in fact a German agent, this claim is patently absurd (especially in light of the fact that Leninism was a major influence in the German Revolution that overturned the Imperial regime). Lenin signed the treaty of Brest-Litovsk which was very favorable to Germany(over the objections of people like Bukharin) but he did this out of necessity not as some sort of reward for Germany's help earlier on.