If you take out sperm in the age of 15 years then the growth would be stopped?

The growth of the 15-year-old would not be stopped, no. It would have no effect on the boy producing the sperm.

Sperm themselves are fully formed upon creation. They are very simple chemically and do not "grow" the way complex organisms do. A male body creates new sperm all the time, continuously. Any that are removed, if kept alive, would be viable.