3. I had had breakfast before I went to work.

--->First I had had breakfast then I went to work 

4. They are reading the books at the present...
--> the books are being read at the moment.

5. She learns English 2 hours a day..
--> English is learned 2 hours a day
--> it takes her 2 hours a day to learn English.
6. Nobody is going to invite her to the party..
--> she is not going to be invited to the party.
7. My mother will buy a computer for me.....
--> A computer will be bought for me by my mother.

8. He was reading a book when I came to visit him...
--> while he was reading a book, I came to visit him