Android phones slow down over time. These steps restore snappiness without rooting.
Clear App Cache
Settings > Storage > Cached data, or per-app under Apps.
Reduce Animations
Developer options > Window/Transition/Animator scale to 0.5x or off.
Disable Unused Apps
Disable pre-installed apps you cannot uninstall.
Lite Apps
Use Facebook Lite, Messenger Lite, and Go edition apps on lower-end devices.