can I downloaded apple app

Not sure what you mean by "Apple App", but there are two apps that might be the best option.

One is the Apple Store App

https://apps.apple.com/us/app/apple-store/id375380948

Two is the Apple Support App

https://apps.apple.com/us/app/apple-support/id1130498044

There are many many Apple Apps.

Which App are you asking about?

To see what Apps are available, tap on App Store on your phone and type in the name of the App that you are looking for.

If you have an iPhone 5s, an iPhone 6 or iPhone 6 Plus......you cannot update to iOS 13 or any other version.

These phones are too old. You will need a new phone to use the apps that you ask about.