UX/UI redesign and prototype for a fully responsive PWA HIIT Timer

I have this tool for myself and friends, a HIIT Timer that allows you to set timers, either a single use one, or a set with rounds, cooldowns, prep times... also I'm planning to add the possibility to sign in/log in, and save/load presets, share them, and the possibility to install it as App (PWA)...

And I want to revamp it, make it look more 2022, so I'll need a UX/UI design and prototype, with current and planned features, non-invasive ads, with a new (or same? doesn't matter to me) color scheme, possibly a logo, the whole rework!