Hi kladrian,
The restrictions article below may explain why you’re running into the issue that’s causing you to enter your Apple ID password each time you download something from the App Store on your iPhone 6.
Use restrictions to prevent purchasing on your iPhone, iPad, or iPod touch - Apple Support
Require a password for each download
If you don't want to prevent in-app purchases or disable purchasing completely, you can require a password for downloads on your device. After you enable restrictions, Tap Require Password, then choose an option.
- Immediately: If you choose this option, you'll have to enter your Apple ID password each time you make a purchase or download a free item.
- 15 minutes: If you choose this option, you'll enter your Apple ID password once, and you won't have to enter it again for any other purchases (except in-app purchases) you make in the next 15 minutes.
Ciao,
-Jason