Past perfect или past perfect continuous
bob wanted to sit down as he (stand) at work all day long.
mary (learn) the poem by the winter.
the rain stopped but there were a lot of puddles because it (rain) cats and dogs. (как из ведра)
susan and jim (chat) via skype for an hour when the connection broke.
they (decorate) the new year tree before the children arrived.
bob (eat up) all the muffins by lunchtime.
my sister (do) the laundry since early morning.
i knew that our parents (grow) melons in their greenhouse since they bought the house.
he (loose) much weight by the end of the year.
brown understood the problems of his agency because he (work) for it since 2005.

1) Bob wanted to sit down as he had stood at work all day long.

2) Mary had learned the poem by the winter.

3) The rain stopped but there were a lot of puddles because it had rained cats and dogs.  

4) Susan and Jim had been chatting via Skype for an hour when the connection broke.

5) They had decorated the New Year tree before the children arrived.

6) Bob had eaten up all the muffins by lunchtime.

7) My sister had done the laundry since early morning.

8) I knew that our parents had been growing melons in their greenhouse since they bought the house.

9) He had lost much weight by the end of the year.

10) Brown understood the problems of his agency because he had been working for it since 2005.