tenses

can someone explain to me the differences among simple past, perfect present tense, and perfect past tense. Give classic examples too.

I went to India. simple past.
I have been to India. present perfect.
I had been to India before I went to Nepal. past perfect.

What, do you think, are the differences in meaning?

I have no idea. What about have had and had had?

I have had a lot of problems in my life.
I had had a lot of problems in my life, until I discovered brand X.