Why you should learn English grammar
My advice as a language teacher is that you spend time studying grammar rules. If you know when to use tenses such as the present perfect, the past simple and the past continuous, your spoken production will be easier to understand. If you want to avoid wasting unnecessary time and money learning endless vocabulary and conjugation lists for specific verbs, then you need a system. Grammar is the repetitive stystem behind the language. If you know some rules, then you will be able to apply them in lots of situations.