Given the numerous issues that a bad update or iOS bug might create, some people may be hesitant to upgrade iOS. This isn't always the case, though. If an iOS update has broken your device, just notify Apple so that they can work on a solution and release a fresh software update with the required improvements. If your iPhone slows down after installing iOS 10.3.3, the iOS 11 upgrade will most likely improve its performance.
Restart your iPhone 6s Plus if it hasn't already.
A reboot provides your iPhone a clean new start and is known as one of the easiest remedies to different gadget troubles. A reboot not only fixes minor software issues, but it also clears your iPhone's memory. Cache files with corrupted contents that may have interfered with your iPhone's regular functioning and operations are also removed.After the reset, thoroughly inspect your iPhone 6s Plus to check whether it has improved in general performance.
Reset all of your iPhone's settings and return it to its original state.
If none of the preceding ways have been successful in speeding up your iPhone, you might try a settings reset. It's conceivable that some of your iPhone's settings files have become damaged, or that a certain programme has been misconfigured, causing your iPhone to slow down. Because tracing down these sorts of issues can be challenging, resorting to a settings reset can assist in resolving the issue. All of your applications, as well as your iPhone's basic settings, are reset when you choose Reset All Settings. As a result, this should only be used as a last option. You'll have to check in to your applications again after the reset.
