If you want to master it perfectly, you have to forget everything you know about English grammar as they differ dramatically. For example, unlike many romance languages, Japanese has only two tenses: past and non-past (present and future). However, there are two forms: polite and plain. The last one is used for casual speech. We recommend that you start to learn Japanese grammar with the help of textbooks.  It’s also important to mention that the Japanese have an entirely different writing system: from right to left, from top to bottom. In these textbooks, you’ll find a lot of practical lessons that will help you get a sense of Japanese writing.