1 and 2 are both good. Maybe 2 is a little better as "buy" implies you pay immediately, whereas "order" means you will pay afterwards. For example: "I order a meal. After I have eaten, I pay for the meal". For 3, you could leave out the "then" - it's not wrong with that word, but it sounds better without it. - "I told the car driver to make a left, and he said okay". For 4, "retrieve" is wrong (also it is not retrive), as retrieve means "bring back". It's better to say "The government officer tried to recover the financial loss" or "The government officer tried to make up for the financial loss".