In the past I used to teach both Polish and English to foreigners of many nationalities. I may assure you that English is
much easier to be learnt for communicative purposes than any Slavic language
Finnish/Hungarian/Estonian seem to be more difficult as far a grammar is concerned, Russian/Bulgarian/Greek - for a different (Cyrillic) alphabet.
Maybe Nebulosa should act expert?
Her English
and Polish have improved significantly over the last couple of years.