I actually learned more about English grammar by studying foreign languages than I ever did before. But I don't think you need to know too much about grammar in order to communicate with other people. Yes, you should learn it if you want to be fluent but it's more important to have a wide range of vocabulary and the confidence to use it than a wide range of grammar but nothing to say. For example, I don't see that it is necessary to learn all the tenses systematically. If you were to say to me "I go to the library yesterday" I would understand that you meant "I went to the library yesterday". Grammatically it's not correct but I'd rather you made the effort even if you didn't know the correct verb form :)

I'm agreement katrina

I don't good in English
any way I will  listen about talk her

The answer depends on the depth of the communication. 

If your topic is simple, even sign language would suffice, so grammar isn't as important.

But if you are talking about something a bit more complex or profound, then it becomes necessary to say it right, as any grey area may cause a great damage.  In that case, grammar is extremely important, as it gives your message the nuances and the subtlety it needs.