Try not to think about learning grammar as some separate thing. You can learn grammar while learning the language. It really depends on what part of grammar you want to learn, are you able to be more specific? If you are talking about tenses: simple past, present perfect, future perfect, and so on, a good idea would be to look up example sentences of these types (most decent grammar explanations include example sentences). Try, as much as possible, to get working examples of the grammar in action, rather than just trying to memorise rules. It works for most grammar stuff too, aside from tenses. Don't learn the rule for something, find the rule being used, either in a natural context or in a grammar book.

Hello, you need a well structured method and a lot of practice!

A good grammar book is the best way. Some people may tell you grammar is not important. Usually these same people cannot ask a simple question correctly and certainly cannot speak using good grammar. Good grammar is essential and must be learned by studying its rules. Here is a list of some grammar topics you should research and master: You should know the capitalization rules: Proper nouns, countries, languages, people's names, day and month names, etc. You should know the punctuation rules for your writing. You should know the eight parts of speech, what parts of speech they modify, and what questions they answer. This will help you determine when you need a noun, adjective, or adverb. You should know that the present tense has three different forms, each of which has specific uses. They are not interchangeable. You should know how to form the six tenses and when to use them. You should know about verb person, number, mood, tenses, and voice, participles, and infinitives. You should know how to use conjunctions (FANBOYS and commons subordinating conjunctions). You should know how to use simple relative clauses (which, that, who, whose, where). You should keep parallelism in mind (A, B, and C should all be the same parts of speech/same tense, etc.). Always use a program that spell-checks.

thank you so much

Hey. Go in a library, take a English textbook and do 3 exercises a day. That's how I proceeded. :)