I want ios14 in iPhone 5s

Hello ~ Your iPhone 5s cannot be updated to iOS 14. It does not have the capacity to be updated further than iOS 12. You need a newer device. If you choose a second hand device click on the links below for some helpful information to avoid any problems…

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Also:

The All Too Common SAD Reality of Buying a Used iPad/iPhone

~Katana-San~

That is not possible, as it is not compatible with iOS 13 or higher.