Witaj! It's about your question about 'no' and 'em'. Em is the "original" preposition to indicate place. Though, "no" and "na" are more specific because they agree with words' genders. Explaining: em + a = na // em + o = no. Then you use "em" when you don't need to use an article right after it. Example: O livro está EM cima da mesa. (The book is on the table). When you need to use an article after the preposition, you must use no or na. Example: Eles falam polandês na Polônia. (They speak Polish in Poland.) // Eles falam português no Brasil. (They speak Portuguese in Brazil). Understand: In English, they dont have genders for words, but in Portuguese, German, French etc, they do. The article (a, o) indicate the gender. PS: It's a short answer that might help you for now, but it's important that you take some time to study prepositions, in any language you're studying.