Learning a Foreign Language and Grammar

Grammar is similar between languages. It is because it is describing abstract, set-theoretic like, relationships, associations between classes of words and not only between the words themselves.

It is this universality of abstract mapping, set-theoretic like associations, relations between classes of words, that needs to be learned so that these abstract constructs can be "filled" later with concrete words.

Grammar uses often exotic names for its concepts e.g. Adjective, Noun, Pronoun, Accusative voice, Antecedent, Adverbial Clause, Apposition, Conjunctive adverb, Gerund, Inflection, Participle, Transitive verb. But, don't be alarmed. Grammar needs this names to describe their abstract set-theoretic relations, associations, relations, mapping.  You are after these abstract relations and not about analyzing why the strange and unfamiliar words are used for the relations components.

You can create your own grammar by specifying markers, references and postulate, form their set-theoretic like mappings, associations, relations. When you define your new words for your vocabulary define classes of words, then you can plug them into your grammar and go ahead with specifying, talking about knowledge or any field. That's how Esperanto is probably made.

There is, probably, universal grammar.

Grammar deals with classes of words. Often banal (in meaning) grammar usage examples show that relations between words classes is what is important. But bundling  words into classes, from different fields, is what makes learning grammar difficult because when "applying" grammar you need to go back - to de-classify the word, i.e. use a SPECIFIC word for the field in question (science, law, medicine, technology, literature). By "classifying" words, putting different fields' words in one bundle, grammar obscures the fields where the words are used. Bundling words is bad but unavoidable.

Grammar cannot teach you creative writing because it describes relations between classes of words. You need to, now, chose a word from a class of words, in your specific writing. This is the opposite process of grouping words into a class and describe the relations between the classes of words, which is what grammar does. Which words you are going to chose is the subject of style and creative writings. Style is a plane, level above grammar. Every field, e.g. science, law, literature, architecture, chemistry, has its own vocabulary whose classes' relations are described by grammar. Which words you choose, say, when writing a novel, is a matter of analysis, art, trial and error, inspiration, intuition, knowledge of the topic.

Good reference How to Use English Articles.