If you want to be online, but want to block internet to certain apps like work apps, messaging apps etc, and continue using rest of your apps, you can do it using this app.
And no,this is not an ad. https://play.google.com/store/apps/details?id=dev.tuantv.android.netblocker
I can do it on my Poco f3 without any app. There is “Restrics data usage” in each app settings.