iPhone 5 on iOS 10 - very slow

Hi all,

Need some help: is it still possible to downgrade from iOS 10 to iOS 9?

Or this feature is closed?

The thing is that I've updated my iPhone 5 to iOS 10 and it became very slow...

Any other suggestions to improve the functionality on iOS 10 (in case of impossibility to downgrade to iOS 9) will be highly appreciated.

Thanks in advance!