Dir, it depends on who is speaking Ukrainian. When it is Timoshenko, I understand everything. We recently watched some movie with Zelensky and Koshevoy in Ukrainian (about divorce) and understood everything. When it is someone from West Ukraine, I understand 20%.
Zelensky is not a Ukrainian at all, but a Jew. Yulia Tymoshenko is also difficult to call ethnic Ukrainian. Her maiden name is Grigyan. For both of them, the Ukrainian language is essentially not native.
I do not see any particular specifics in the language of Western Ukrainians. There use a dozen of everyday words from a local dialect, and nothing more. And their spoken Ukrainian language is much more correct and adequate than that of residents of Kiev or the east of Ukraine. And I think that's why you don't understand them well.