I want to practice English but I'm always confused because of the grammar. I don't know how to use "had been. have had done. have been" and so on. I cancould learn English well if it is grammar were unnecessaryto learn grammar, but this is impossible so I'll just be study hard.

Alternatively I would say, I could learn English well if grammar weren't necessary...

Had been or have been, is past tense for having gone somewhere or done something.

I had been to the circus as a child. (as a child = when I was a child) same meaning.

I had been all over the world and experienced many things.

I have been doing fine on my own.

Have, (present tense) I have many friends (presently).

Had, (past) I had many friends (but now I don't). (had, used to have)

Done, (past) I've done my homework. (done, completed, finished) etc.

You're English is very good, I hope this helps. ^.^v