Notifications taking too long to come through

Hi,  please could you tell me and fix an issue with notifications taking too long to com through.  I regularly speak to a friend and when I get a notification about her message, it’s usually been a few minutes, this evening for example I got a notification and when I checked the message , it said 6 mins has passed, it is really annoying to keep refreshing the chat to catch the person live.  Can you make it more live like WhatsApp?  This is the same for games also.