Question marked as
Sorry, iPhone 6 is an outdated iPhone it can’t be update to a higher iOS (13 and later).
The last security updates iOS 12.5.7 -> released September 12, 2022, available for iPhone 6.
Check iPhone model & iOS version -> Go to: Settings -> General -> About.
Yes, most apps require iOS 13 or later.
Considering a newer type of iPhone?
Read before you buy a newer iPhone: The All Too Common SAD Reality of Buying a Used iPad/iPhone
The All Too Common SAD Reality of Buying … - Apple Community
Apple Store -> iPhone - Buying iPhone - Apple
Apple Certified Refurbished -> Refurbished iPhone Deals - Apple