i need IOS 13 update my device iphone 6 becouse same apps not working my device

See the Apple Support article(s) below. 

iOS 14 and iPadOS 14 Compatible Devices

iOS 13 and iPadOS are compatible with these devices - Apple Support.    

You would need to get a newer device. An iPhone 6 cannot be updated beyond iOS 12.

Anything that is capable of running iOS 13 is also capable of running iOS 14. Since the iOS update system only ever allows installing the most recent version compatible with the detected hardware, no device will ever be offered iOS 13 as an update. It is a discontinued release now. Devices that support(ed) iOS 13 will only have the option now of iOS 14.4.

Your 2014-era iPhone 6 has half the memory of an iPhone 6s, and a quarter of the memory in an iPhone 12.

Not enough memory, and not enough processor capabilities, for newer iOS versions, and for newer apps.

iPhone 6 to iPhone 6s was both a memory upgrade and a processor upgrade, and not a small increase.

For newer software and newer apps, you’ll need a newer or new iPhone.