PWA using javascript, indexed db, service worker

I am trying to make a PWA with the help of IndexedDB and Service worker. I got a tons of tutorials refered below

https://www.monterail.com/blog/pwa-working-offline https://css-tricks.com/making-your-web-app-work-offline-part-1/ https://pspdfkit.com/guides/web/current/pspdfkit-for-web/create-offline-progressive-web-applications/

everywhere or other I was stuck, because, there was already developed code which did not build, or i could not install any depnency packages [could be firewall blocked them] ...

What I want to do is do some CRUD operations (lets say i will use json-server) and read all the employees when online and offline. similarly i want to do CRUD both online and offline, if i do CRUD offline, it gets synced when I get online.

Is it too much code to accomplish this ? Love to read a tutorial which starts from ground up and does this. yeah I am feeling like a struggling developer, but then hoping SO / internet to help me while i still trying to make it work.

Another question is, what happens when I hit the link of my PWA very first time and internet is not available ?

thanks a lot