created three separate button js files: restart, start and pause; then create watch js file; this file will render three buttons js files; watch.js will have constractor, function for start stopwatch , pause stopwatch and restart stopwatch; start stopwatch function will use setInterval() to update the state every second; restart stopwatch function will set all the states to default; pause stopwatch will clearInterval or if pressed again continue timer;

1. https://reactjs.org/ - Components
2. https://upmostly.com/tutorials/setinterval-in-react-components-using-hooks - setInterval in React Components Using Hooks
3. https://scotch.io/@micwanyoike/how-to-add-fonts-to-a-react-project - How to add Fonts to a React Project