- I joined this activity as a volunteer work.
- I volunteered to join this activity.
- I volunteered to do this work.
Japanese needs nouns because you can only attach the 助詞 to nouns.
The global average TOEFL speaking score is 19. The Japan average score is 15. My students' average top TOEFL speaking score is 23. Why? Because they don't use templates! If you have a clear voice and practice regularly, you should get 23 consistently too.