Translation of quicksilver in Spanish

A bystander who watched the entire scene all the time decided to help me. He was an older man, around seventy, but nonetheless he went to the oldest of these kids and slapped him. The boy was sixteen.
Life here is the opposite of what you think. We are living in small village which is a housing complex for MCD employees with their families. It's a children paradise and on the other hand quite boring.
We checked in, took a refreshing hot shower and were really happy about our accommodation. As it was late, we took another ride to some restaurant. When we payed the driver he told us that he had no change.