It's a pity they are travelling on uncomfortable buses (wish)
-->I wish they weren't travelling on uncomfortable buses.
We haven't used these machines for a long time
--> it's the first time we have used these machines for a long time.
He last saw his grandfather 2 years ago,didn't he?
--> he hasn't seen his grandfather for 2 years.
The last time I used that bike was 2 years ago
--> That bike hasn't used for 2 years.
He said that "I can do these exercises in fifteen minutes"
--> He said that those exercises could be done by him in fifteen minutes.