How can I update my iPhone 📱 6s And my battery die fast

Please see: Update your iPhone, iPad, or iPod touch - Apple Support

And: If your iPhone, iPad, or iPod touch won't update - Apple Support

If the above Apple articles do not help, please post back with relevant information. 

Bella ~ Does your iPhone 6s Plus still have its original battery?

And what's the Maximum Capacity % here?...

Settings > Battery > Battery Health

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