problem with notifications on android 7.1.2

Question

Hi, I have a Nokia 5 cell phone with the latest update of Android 7.1.2.
my problem is that when someone sends me a message either on Facebook, Instragram or WhatsApp it takes a long time to reach me instantly (sometimes it takes about two hours to get the notification) the only way I can see the messages who sent me before the notification is to enter the app but I can not be all day checking if someone sent me a message, please help
P.S. I have all the applications updated

Answer 1

Do not download applications that save RAM or that clean cache automatically, there are apps that help you kill all processes in the background. If so, undo it, but before doing so, delete the app's cache and data, then undo it

Answer 2

You have to review the permissions for the app that fail, it is a problem of notifications and permissions for the version of android that you have, another option is to reinstall the app in question, so that the system asks for the permissions, you give them and it would return all to normality ..

Answer 3

Check also in "data usage" that you do not have the option to restrict background or background data of certain applications that are failing you. It happened to me once with the whatsapp and I did not activate it ... I dropped and everything OK.