1. Thank you for helping me.
=> It was kind of you to help me.
2. No, please don't tell him.
=> I'd rather you didn't tell him.
3. A mechanic serviced my car last Sunday.
=> I had a mechanic service my car last Sunday.
4. I had no map, so I got lost.
=> If had had a map, I wouldn't have got lost.
5. I don't have money, that's why I can't lend you.
=> If I had money, I would/ could help you.