31. the difficult test/ the difficulty/ the fact that is was difficult.   

32. encountering difficulties, he always studies hard.

33. I don't know Russian, i've had to have a document translated into French.

34. the dark, they continued to work.

35. getting an English name, he is in fact German.

36. these students had an accident, they arrived late.

37. being lazy, Nick is often punished.

38. its small room.

39. he was negligent in his driving, the accident happened.

40. getting paid extra, Karen works on Sundays.

$^-^$

=>
31. I couldn't do the test because of the difficult test.
32. Despite enountering difficulties, he always studies hard./Despite his difficulties, he always studies hard.
33. Because I don't know Russian, I've had to have the document translated into French.
34. In spite of the darkness, they continued to work.
35. Despite having an English name, he is in fact German.
36. Because these students had an accident, they arrived late.
37. Because of being lazy, Nick is often punished.
38. We bought the house despite íts small rooms.
39. Because he was negligent in his driving, the accident happened.
40. Because of getting paid extra, Karen works on Sundays.