1. Please speak to the concerned clerk.
Ans: Please speak to the clerk concerned.

2. you have got time too short for that.
Ans: You haven't enough time for that.
or
Time is too short for you to do that.

3. Not only he was a thief, but he was also a murderer.
Ans. Not only he was a thief, but also a murderer.

4. They thought that the plan would be succeeded.
Ans: They thought that the plan would succeed.

5. It is unlikely that he wins the race.
Ans: It is unlikely he wins the race.

6. My uncle has told me something about it yesterday.
Ans: My uncle told me something about it the previous day.

7. I hoped that by the time I would have got there it would have stopped raining.
Ans: I hoped that by the time I had gotten there it would have stopped raining.

8. They prevented the driver to stop.
And: They prevented the driver from stopping.

are these correct?