why i need the wifi to be connected always because i am using desktop WhatsApp App. and it got disconnected when the internet is off on my phone.
Try wifi, advanced setting, turn on wifi automatically setting to off.
sleep option has been removed so you can try to disable optimise settings under device care/advanced and see if that hopefully makes a difference and/or go adb route
https://www.androidpolice.com/2017/...y-removed-keep-wifi-sleep-toggle-pixel-2/?amp