If you speak Spanish, some English grammar rules will feel natural and others will feel confusing. These are the biggest differences to focus on first.
Spanish uses Subject-Verb-Object like English, but adjectives come AFTER nouns. 'Red car' in English is 'carro rojo' (car red) in Spanish. This often causes Spanish speakers to place adjectives incorrectly in English.
Spanish has 4 articles (el, la, los, las) based on noun gender and number. English only has 'the', 'a', and 'an' with no gender system at all.
Spanish conjugates verbs differently for each pronoun and has 14 tenses compared to English's 12. The Spanish subjunctive mood is used far more frequently than in English.