@danidend typically a PWA would include a front end written in JS and this would be embedded in html.
The key part of a PWA is for it to be aware of whether you are 'online' or not, and this will be handled by a serviceworker. If the serviceworker detects no connection then methods like form posting and page changes are blocked until you get your connection back.
If you've got an existing app, written in js and talking to your backend via axios or similar then changing this to be 'online aware' is pretty trivial.
If you haven't built like this then you'll need to post what you have got before anyone can really help with how to adapt it.
This tutorial should give you an idea of the minimum you need to be classed as a PWA. https://codebysamgan.com/how-to-create-a-progressive-web-app-pwa-in-laravel-5/