Can you check these last sentences? Thank you, Writeacher!

1) He is learning to drive a moped.
2) I'm teaching him to speak French.
3) I wonder whether to reply to his email or not.
4) We were obliged to postpone the meeting.
He was the first to hand in his test.
He is the best student to speak English.
5) To begin with, I'll have tomato soup.
She threatened to dismiss me if I didn't tell the truth.
He arranged for his friends to have lunch in a restaurant.
6) She pretended not to know us.
They have decided to invest all their money in shares.
She failed to answer all the questions. She didn't manage to answer..

All are fine.