1. ＊They were driving when I went to see them yesterday.
2. ＊It rains here very often in Taipei.
3. ＊He gave his book to his brother last month.
4. ＊He goes to work every morning.
5. ＊He likes to tell stories.
6. ＊I like to go to church.
7. ＊The sun set now. (I would say 'The sun is setting.' OR 'The sun set just now.', depending on if it's a past action or a present progressive action)
8. ＊They are playing the piano now.
9. ＊I love you.
10. ＊He was a good student before.
11. ＊He went to the church last Sunday.
12. ＊It rained last night.
13. ＊I was playing when you called.
14. ＊It was raining when I drove to work last night.
15. ＊He does not know me.
16. ＊I was swimming when my mother came.
17. ＊They are singing now.
18. ＊He does not like to swim.
19. ＊He always wears a black coat.
20. ＊He is watching TV now.
I only found an error with number 7. Other than that, this is perfect! Well done!