My iPhone 5s goes really slow most of the time and it's on iOS 9.2

Apps won't update:

Turn your device off and back on. If this doesn't help, sign out from your account and sign back in.

Slow iPhone:

Try to reset your device. This won't delete your data stored on this device.

• Press and hold the Sleep/Wake button
• Press and hold on the Home button
• Keep holding both buttons until the display turns off and back on with Apple logo on it.

Alternatively, you may go to Settings - General - Reset - Reset All Settings

If this does not help, restore your device to factory settings. Note that this will erase the data from your device.

Take a look this Apple Support article: Use iTunes to restore your iPhone, iPad, or iPod to factory settings - Apple Support.

Battery drains faster: Battery Saving Tips for Your Beloved iPhone

Hi

Go to settings turn OFF apps refresh that will save battery .

Also try a reboot press & hold power button & menu button

Hold both down until you see apple logo .

This can take 30 seconds .

Cheers

Brian