Of course you do, Think of English vocabulary as the bricks of the language and grammar as the mortar that hold those bricks together, without the mortar the bricks can come tumbling down! A lack of grammatical skills can cause embarrassing misunderstandings.

When you begin to learn English, speaking and building up your vocabulary is more important than worrying about correct grammar. However, as you progress you need to incorporate more grammar into your learning programme. At an advanced level you should be thinking much more about the correct use of the English language.

There is a common impression that learning English grammar is painful, but it is a lot easier than many other languages. Of course, English is more than just memorizing grammar rules, the grammar must be incorporated into the everyday use of the language, theory and practice should go hand in hand.