For those with delay notifications, just sharing some steps to minimize it:
1) Settings - Notifications - Manage notification - Select app - Priority ON
2) Security - Permissions - Autostart - Select app ON
3) Security - Data - Restrict data usage - Select app - Data/WLAN on
4) Security - Data - Data saver OFF or Deselect apps
5) Settings - Additional settings - Battery & Performance - Manage apps battery usage OFF or Deselect apps
6) Menu (left button) on home, hold app icon & pull down to "lock" app
7) Reboot phone daily, and start those daily app manually
and yep its mostly due to MIUI system which allows multiple customizing/optimizing thats affecting all the push notifications