But do sentences like this exist in Russian and still make sense?

All the faith he had had had had no effect on the outcome of his life

In reality I don't think there's anything unique to English that makes it difficult and there's definitely languages that are far harder to learn.

But I think for some people it can be confusing because it's not very well structured. Or the structure changes depending on the words being used due to our history of amalgamating random words and phrases from other languages without "anglicising" them. Then there's the issue of rules, where no rule actually is universal, there's exceptions to every single grammatical and spelling rule in the language.

So we have lots of instances of things like the past tense of teach being taught, but the past tense of preach being preached and while Vegetarians eat vegetables, people who eat fish aren't Fishatarians, they're Pescatarians, people who eat humans are cannibals, not Humanitarians.

Then you have things like Hamburgers not actually having ham in them, Pineapple's contain neither pines, nor apples and Killer Whale's are dolphins that kill whales.

Again, none of this is unique to English. But it's the collection of all these things together, I think, that makes English difficult to master. It's easy to get a grip on and it's easy to get by with, but it's almost as if it were designed to be a "gotcha!" language, I don't know many British people who feel fully confident with