The button on the pinetime uses 2(!) GPIO ports.
This sample application displays “a LED”; Long Press on the button and the LED changes “color” Short Press toggles the LED.
Several messages are printed to the serial port. In order to view these you will need a segger JLink probe (RTT).
pinetime segger jlink debugprobe
west build -p -b pintime_devkit1 samples/button/pinebutton