Cut unnecessary bytes. Compress everything, strip unused code, be wise when adding dependencies
Split code by routes. Load only what’s really necessary right now and lazy-load other stuff later
Cache code. Some parts of your app are updated less often than other ones. Separate these parts into files so that they are only re-downloaded when necessary
Webpack is not the only tool that could help you make an app faster. Consider making your application a Progressive Web App for even better experience and use automated profiling tools like Lighthouse to get improvement suggestions.
Don’t forget to read webpack docs – they have plenty of other useful information.
And make sure to play with the training app!