Verified answer

13 was, had already set (считаю, что sit - это опечатка или ошибка)

14 did you hear, - I heard it (the news - ЕДИНСТВЕННОЕ ЧИСЛО!)

15 are you doing, am writing, did you receive, received

16 Has your son already done his lessons (еще одна ошибка)? - Yes, he has just finished... he is watching

17 Is it raining now? - No, it stopped raining... the sun is shining

18 has learnt, is translating

19 Has your child got... he got it

20 It's time to go. Have you finished your work?