If you use Safari often on your iPhone you may have tabs open in the background, perhaps slowing down your phone. Following is a tip that might be helpful. Also, it's quite helpful to close apps that might be running in the background, and consuming memory. Put a finger on the app, it will turn small, and you can just 'flip' it up and away to close it.
Jim Hamm
Do this now to speed up your phone
Maybe you keep your computer browser nice and tidy (good for you!), but I bet your phone’s browser is a complete mess. Those tabs running in the background eat up valuable memory. There’s an easier fix than closing tabs one at a time.
On iPhone:
Open Safari. Tap and hold the icon that looks like two overlapping squares. From the pop-up, choose Close All Tabs. Done!