Why can't I install apps on my iPhone?

Hello~ The screenshot message you posted indicates that it was refunded or purchased on another Apple account. You are also in need of a newer model iPhone as the iPhone in your tagline indicates your are using a device that can’t be updated any further than the current version of iOS 12. To shop for a new iPhone…

Buy iPhone - Apple

Refurbished iPhone Deals - Apple

If you choose to buy from a third party …click on below and review in order to make an informed decision…

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

~Katana-San~

Your tagline indicates that you are on iOS 12 and in the screenshot it shows that it requires iOS 15 or later. The message also indicates it may have been previously downloaded with a different Apple Account, but that is irrelevant as you will not be able to update or download the app anyway.

Hello~ Any help clicking on below and reviewing the information found there?

If you can’t download or update apps on your iPhone or iPad - Apple Support

~Katana-San~

What happens when you try?. You will find that many developers no longer support iOS 12, so what is offered in the App Store may be limited. Each Developer chooses which iOS versions they want to support.