11. at last the librarian (to give) me the book which i (to wait) for during two months. i was very glad. i (to go) home and (to begin) reading it at once. 12. don't speak to him: he (to be) very busy, he (to do) some very urgent work.

11. At last the librarian gave me the book which I had been waiting for during two months. I was very glad. I went home and began reading it at once.
12. Don't speak to him: he is very busy, he is doing some very urgent work.