If you speak Polish, some English grammar rules will feel natural and others will feel confusing. These are the biggest differences to focus on first.
Polish word order is flexible because grammatical cases show the role of each word — you can move words around and the meaning stays clear. English word order is strict because position determines meaning. Polish speakers often produce technically incorrect English word order.
Polish has absolutely no articles. English articles 'a', 'an', and 'the' express definiteness and specificity — concepts Polish handles through context and word order. Articles must be learned from zero.
Polish aspect — perfective and imperfective — must be expressed in English through tense choices. Polish also has past tense verb forms that change based on the grammatical gender of the speaker. English verbs have none of this complexity.