If you have had your device for a while and it is not working well, then resetting it may put it right back into good shape.
This applies to computers in general and smartphones as well.
When you go to settings and tap on reset, you get the option to keep your apps and other information. I generally keep only selected apps where I have that option.
So many of us forget to do the reset procedure, just as we forget sometimes simply to pull the plug and reinsert it to restore functionality.
Resetting does take some time, so don't panic!