I'm having trouble rewriting the ambiguous sentences. I have answered them but i'm not sure that they are right.

2. Please close the door behind you.
My answer: Please close the door that is behind you.

3. we heard that he informed you of what he said in his letter.
My answer: We understand that he has written a letter, and that he has told you about the contents of the letter.

5. Charles drew his gun.
My answer: Charles took out his gun.

9. Tuxedos Cut Ridiculously!
My answer: Prices on our tuxedos have been drastically reduced.

15. Don’t freeze your can at the game.
My answer: don't throw your can at the game?

21. We’re going to look at lots this afternoon.
My answer: We are going to look at a lot of things this afternoon.

24. New york’s first commercial human sperm-bank opened Friday with semen samples from 18 men frozen in a stainless steel tank.
My answer: New York's first Commercial sperm-bank opened Friday. 18 men gave semen samples, which were frozen in a stainless steel tank.

27. Abraham Lincoln wrote the Gettysburg address while traveling from Washington to Gettysburg on the back of an envelope.
My answer: While traveling from Washington to Gettysburg Abraham Lincoln wrote the Gettysburg address on the back of a envelope.

29. In one of Shakespeare’s famous play’s, Hamlet relieves himself in a long soliloquy.
My answer Hamlet calms himself by reciting a soliloguy.

38. Please do not feed the animals. If you had any suitable food, give it to the guard on duty.
My answer: Instead of feeding the animals give any suitable food you may have brought to the guard on duty.

3 answers

2. Please close the door behind you.
My answer: Please close the door that is behind you.
I'd write: Please close the door after you leave. (or "after you come in."

3. we heard that he informed you of what he said in his letter.
My answer: We understand that he has written a letter, and that he has told you about the contents of the letter.
Wordy! I'd write this: We heard he told you about the contents of his letter.

5. Charles drew his gun.
My answer: Charles took out his gun.
I agree.

9. Tuxedos Cut Ridiculously!
My answer: Prices on our tuxedos have been drastically reduced.
I agree.

15. Don’t freeze your can at the game.
My answer: don't throw your can at the game?
I would write this: Don't freeze while sitting and watching the game. ["can" is often slang for "your bottom"!!]

21. We’re going to look at lots this afternoon.
My answer: We are going to look at a lot of things this afternoon.
I'd write this: We are going to look at several pieces of property this afternoon. ["lots" = land]

24. New york’s first commercial human sperm-bank opened Friday with semen samples from 18 men frozen in a stainless steel tank.
My answer: New York's first Commercial sperm-bank opened Friday. 18 men gave semen samples, which were frozen in a stainless steel tank.
I'd write this: New York's first commercial sperm-bank opened Friday. Eighteen men gave semen samples, which were frozen in a stainless steel tank.

27. Abraham Lincoln wrote the Gettysburg address while traveling from Washington to Gettysburg on the back of an envelope.
My answer: While traveling from Washington to Gettysburg Abraham Lincoln wrote the Gettysburg address on the back of a envelope.
I'd write this: While traveling from Washington to Gettysburg, Abraham Lincoln wrote ...

29. In one of Shakespeare’s famous play’s, Hamlet relieves himself in a long soliloquy.
My answer Hamlet calms himself by reciting a soliloguy.
I agree with "calms" as a good substitute for "relieves"!!!

38. Please do not feed the animals. If you had any suitable food, give it to the guard on duty.
My answer: Instead of feeding the animals give any suitable food you may have brought to the guard on duty.
I'd write this: Instead of feeding the animals, please give the guard any suitable food you may have brought.
Thank you, I think that I was being to wordy with my answers.
Sometimes we get that way ... then it takes someone else to help us weed out the extraneous stuff!

You're welcome!