Hard situation puzzles

A person called the police and told them to ask about John K. Upon arrival at John’s house, the police found him dead. Examining the corpse, the police discovered severe injuries. But the apartment was in perfect order, without any signs of a struggle or break-in.

A woman starves to death despite being surrounded by food.

A woman misread something and never saw another person again.

The woman is speaking something and she is upset. Nobody can understand her but a man is filming her on camera. Why? And what is happening?

A man designed a device into which you can insert colored paper, and then get the ideal 100$. Experts can not distinguish them from the real ones. How does he do that, and why does he sell this device?

A woman asks questions to her friend - a policeman - about a strange death. After 5 minutes the policeman is surprised to see that the woman finds out the cause of the death.

Eva was a skeptic, and never believed in the paranormal. But after she had spent 3 nights in a creepy forest all alone, her skepticism disappeared. Why?

He wasn’t hungry, but food saved his life.

A professor didn’t want to accept a student’s paper. Student: “Do you know who I am?” Professor: “I neither know nor care. And don’t try to frighten me!” But the professor still accepted the paper. Why?

Bill always wore a silk scarf to work, whatever the weather. What’s his job, and why does he need this scarf?

Gordon came to see Harry and gave him a few strikes in the stomach. Then, they had a short talk, and he struck a few more times. Harry died a couple of days later. What happened?

A coin collector finds an internet advertisement about a coin collection at a very low price. After reading it carefully, he decides to buy it. Although it is genuine and its value is much higher than the price he pays, he is not happy but very angry.