COUNTDOWN AND COUNTUP TIMER USING ARDUINO

I need some help for coding. "Everytime that there's an input(pushbuton) the timer will add 5 mins. and it will countdown. When it becomes 0 for a certain delay in time like 30 secs. The timer will count up... Then you need to input again to make it 0." the timer will be shown in a
LCD 1602 Display for Arduino Blue Module
This will really help me

What have you done so far ?

Is this a school assignment ?