Using gerund phrase

[Allifathima]

1a. He liked the idea of going to Moscow in May.
1b. He liked the idea of us/our going to Moscow in May.
2a. I know of his having helped you.
2b. I know of him helping you.
2c. I know he helped you.
2d. I know that he has helped you.
2e. I know about him helping you.
3a. His listening to English is very bad.
3b. His reading of English is very bad.
Please correct all the above sentences.
Thanks.

[Beeesneees]

1a. He liked the idea of going to Moscow in May.
1b. He liked the idea of us/our going to Moscow in May.
2a. I know of his having helped you.
2b. I know of him helping you.
2c. I know he helped you.
2d. I know that he has helped you.
2e. I know about him helping you.
3a. His ability to listen/skill of listening to English is very bad.
3b. His reading of English is very bad.
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