Hello Harve55,
If your iPhone 4s is acting sluggish or slow to respond after an iOS update, here are a few things you can try to improve performance:
https://support.apple.com/en-us/HT201559
To force restart your device, press and hold both the Sleep/Wake and Home buttons for at least ten seconds, until you see the Apple logo.
https://support.apple.com/en-us/HT201330
- Press the Home button two times quickly. You'll see small previews of your recently used apps.
- Swipe left to find the app you want to close.
- Swipe up on the app's preview to close it.
iOS 7 and later uses a parallax effect to create the perception of depth on your Home screen and other areas of your device. When parallax effect is on, you might notice:
- Screen zooms when you open folders or apps.
- Wallpaper icons and alerts shift slightly when you move your iPhone, iPad, or iPod touch.
- Photos or images you use as a wallpaper are slightly zoomed in or can't scale to fit the screen.
You might also see motion in apps like Weather and Messages. To reduce these types of movement, go to Settings > General > Accessibility, and turn on Reduce Motion.
Another setting you can turn off is Background App Refresh. The resource below explains how to turn it on, but if you have it on, you may want to turn the feature off to see if performance improves.
https://support.apple.com/en-us/HT202070
If you don't want suspended apps to check for new content, go to Settings > General > Background App Refresh and turn off Background App Refresh.
Harve55, If these changes don't improve your iPhone's performance, you may want to backup your iPhone and restore it from a backup. A final option would be to restore the iPhone as a New device.
https://support.apple.com/en-us/HT204686
Take care,