As a Russian who is hosting Ukrainian refugees I can definitely say this is false. I can understand probably around 90% of raw speech in Ukrainian without any support and 0 prior experience.
Yes, there are lots of family and friendship ties between the countries. It's sad that Putin has destroyed any chance of good relationships in the future, and basically solidified Ukraine as a nation in opposition to his aggression.
If you don't have time to watch all 23 episodes, the last one is a bit of a summary, discussing the history of European imperialism and colonialism, particularly Nazi German imperialism (conquering Ukraine was a central strategic goal of WW2), and pointing out some European hypocrisy in their reckoning of this history, and how Russia is exploiting that to pursue its own imperialist and colonialist goals.
Here’s a good video to help clarify things for you. https://www.youtube.com/watch?v=CQLM62r5nLI
https://en.m.wikipedia.org/wiki/List_of_invasions_and_occupa...
Even Russia is very diverse ethnicaly and culturaly, as expected of such a huge country. The differences between the Far East, Sankt Petersbug, Daghestan and Buryatia are quite significant.