I have just seen aaw the movie ' A secret life'.

I understood the whole,but there was some sentences are still difficult .

I understood the complete story, but some sentences were difficult to understand.

I think if would see it over and over again.I getting a results.

I think, if you see again and again, you would understand it better.

I have just seen athe movie, ' A sSecret lLife'.

Since you are mentioning something specific it is better to use "the."

I understood it/the wholefilm,but there was some sentences are still difficult peech that was difficult to understand.

I'd say speech here because it is spoken, whereas sentences are what one sees written.

I think if I would see watch it over and over again.I getting a, I would get good results.

I am not sure if you mean, "if I did such and such a thing, I would achieve this or that thing" .. or if you mean, "I think I would like to watch it over and over again. I am getting results."