For correct work of application:

1) In “Phone manager ⟶ Settings ⟶ Battery” turn OFF “Power saving mode” and “Ultra power saving”.

2) In “Settings ⟶ Battery ⟶ Launch” turn OFF option “Manage automatically” and turn ON options “Autostart”, “Work in background” and “Indirect start” for Prof Reminder.

3) In “Settings ⟶ Apps ⟶ Permissions ⟶ ⋮ ⟶ Special access ⟶ Battery optimization ⟶ All apps ⟶ Prof Reminder” select “Don’t allow”.