Arduino coding

Hello, I'm working on an arduino project and i need someone to correct my code and add some lines.

The goal is to start and stop an engine via an android app ( mit app inventor ) and keep it at steady rpm (50hz) thanks to servo motor which is connected to throttle ,replacing the governor. A hall sensor is mounted above the flywheel.
One relay for starting, another for stop, servo and hall sensor work together to stay at 50hz.

I have uploaded the code i currently have.

Thank you for taking the time for reading my post, greetings.