nec投影仪灯泡灯闪烁 Simple Timer 5 min, 10 min. and 15 minute. New to Coding

Hello i need help for this project to become possible. I want to build a timer/ multiple timer for 5 mins,10 mins and 15 minute.

case 1:

if button1 = HIGH;

runTimer 5 // Run timer for 5 minute

digitalWrite(LEDpin1, HIGH); // Turn LED ON while Timer is running

else

digitalWrite(LEDpin1, LOW); // Turn LED OFF when timer reaches to Zero.

case 2:

if button2 = HIGH;

runTimer 10; // Run timer for 10 minute

digitalWrite(LEDpin1, HIGH); // Turn LED ON while Timer is running

else

digitalWrite(LEDpin1, LOW); // Turn LED OFF when timer reaches to Zero.

case 3:

if button3 = HIGH;

runTimer 15 // Run timer for 15 minute

digitalWrite(LEDpin1, HIGH); // Turn LED ON while Timer is running

else

digitalWrite(LEDpin1, LOW); // Turn LED OFF when timer reaches to Zero.