From the frontend, you should try to master Chrome DevTools (or other tools if for some reason Chrome isn't ok with you).

There's pretty much everything you need in there:

- Emulate devices for design and testing

- Track network traffic

- Step by step debugging out of the box

- Performance diagnostics

- Inspection of the DOM tree with real-time replacement of CSS and HTML for UI development and debugging

- Plugins for React and other frameworks