How to start Activity

A question from a novice developer. I have an application that should display the distance traveled during an activity, the duration of the activity, and the distance covered between two presses of the LAP button (pressing LAP resets the distance counter). My question is: how do I start the activity using the START/STOP button? In the simulator, after starting the simulation and pressing the Start button, everything works as expected.

However, on the Fenix 3 watch, I don't know how to start the activity...You may find source code in GitHub: https://github.com/wojciewa/OrienteeringApp

Regards

Wojciech W.