Sir my apple store is iphone 6plus device it is not getting updates and when I open the App Store the app will be not installing plz give me solutions

iOS 12.5.6 is the latest iOS security update for iPhone 6 Plus

iPhone 6 Plus is an outdated iPhone it can’t be update to a higher iOS (13 and later).

Yes, most apps require iOS 13.4 or later.   

De solution is you can upgrade to a newer iPhone type.                             

Considering a newer type of iPhone?

Read this before you buy a newer iPhone.