for React projects, I would use codesandbox: it will give you a more real-life environment, e.g. you can create different files for different components, you have a linter; this is especially cool when you have a local project: you put it on Github and can import it on codesandbox, no need to copy and paste or keep stuff in sync
I’d remove the magic numbers: the number 60 is 19 times in your js code, 25 3 times; without knowledge what a pomodoro timer is, this will increase the need for cognitive energy
I’d move helper functions like padTime, getMinutes and getSeconds into a folder utils or helpers, maybe other components (in a bigger project) would need these functions too; this is only personal preference, no need to overengineer your code
Overall great work,
looking forward to seeing your next steps.