He made a drug that could separate the good from the evil (meaning: the good and evil side of human personality)?
A few days later/after/ afterwards?
He transformed into Mr Hyde
He transformed himself into Mr Hyde?
While she was sitting on the bus she was asked to leave/give up her seat to a white man
The cat smashed the clock through the window/ The clock smashed through the window?
The clock fell off the window and landed on the car roof
He cut the rope and let his friend fall
(left his friend fall is wrong?)
Can you tell me if the above sentences are correct?
You wrote --
He made a drug that could separate the good from the evil (meaning: the good and evil side of human personality)?
I'd write, "He made a drug that could separate the good and evil sides of the human personality.
A few days later/after/ afterwards?
I'd use "later" or "afterwards."
He transformed into Mr Hyde
He transformed himself into Mr Hyde?
I'd use the second sentence, but without the question mark. Period there instead!
While she was sitting on the bus she was asked to leave/give up her seat to a white man
Comma after "bus," and "give up" for the word choice. Also a period at the end of the sentence.
The cat smashed the clock through the window/ The clock smashed through the window?
Maybe this: "The cat caused the clock to smash through the window."
The clock fell off the window and landed on the car roof
I'd write, "The clock fell out of the window and landed on the car's roof." (This isn't the same clock that the cat bumped, right?)
He cut the rope and let his friend fall
OK, but it needs a period at the end of the sentence.