Grammar is important in all languages. I listen to Spanish lessons that say "without grammar, our Spanish would fall into pieces!" I don't think it has any extra importance in English. Do you think grammar is the most important part of learning Hindi? I think it is important to practice using a language--reading, speaking, and listening. I would NOT try to learn grammar FIRST. I would not put extra emphasis on it. I would mix it in with all the other ways of learning. When we learn our own native language, we "learn by doing." We learn to speak it fairly grammatically, long before anyone teaches us any rules.