How do you think that learning languages without grammar?

I think It's necessary to learn grammar.

But some people claim that you can learn English without learning grammar.

How does it work without it?
There are many ways to learn languages easier which is that I haven't known yet?

I'm still not good at grammar despite of that I've been studying English hard.

I've been thinking that the more i study grammar, the more i improve and better my English.

But when I heard that theory I'm confused.

I guess some exceptional person's prove give me a clumsy hope.