Can you convert the number zero(0) into a positive number using just one mathematical operator ?

In a football game, Christina defeated Teresa by 2 - 0 but no man from either side scored. How can this be possible?

A bomb goes off.
Carnage.
One person, only a few feet away, survives! How can this be?

No one wants to have it, but if one got it, he does not want to lose it. What is It?

John walks into the daily grocery shop and steals a $100 bill from the shop. An hour later John returns to the shop and buys some daily products for $40. John pays the owner the $100 bill and therefore the owner returns him $60.

How much money did the owner lose?

After a heavy Thanksgiving meal, the night watchman went to work. In the morning, he told his boss he had dreamed that a saboteur planted a bomb in the factory and that he felt it was a warning. The boss promptly fired him. Worker confused, Why boss fire him?

A thief enters a store and threatens the clerk, forcing her to open the safe. The clerk says, “The code for the safe is different every day, and if you hurt me you’ll never get the code.” But the thief manages to guess the code on his own. How did he do it?

A Scientist was fifty years old in the year 2000 but he was forty years old in the year 2010. How can this be possible?

PS: It has a logical answer.

A man was gazing through the window of the 23rd floor of the building. He suddenly opened the window and jumped on the other side of the window. On landing on the floor, there was not a sheer mark of injury on him.

How can that be possible if he did not use any kind of parachute and did not land on a soft surface?

A pond had 60 fish, out of which, all but 20 died.
How many fishes are now present in that pond?