Grammar is the backbone of a language and without it any single thing you know may be flux, in a sort of jelly without much consistency. In a nutshell, grammar provides you with the structure you need in order to organize and put your messages and ideas across. It is the railway through which your messages will be transported. Without it, in the same way as a train cannot move without railways, you won’t be able to convey your ideas to their full extension without a good command of the underlying grammar patterns and structures of the language.
So, by this theory we can conclude by saying that grammar is undoubtedly the most important ingredient of learning English.
Hope it was helpful... :):):)