Sindar is having trouble with his Samsung Galaxy Note II running slow. Leo says that it's always a good idea to delete everything, and do a factory reset to see if that helps. Also, the more apps he has, the less storage he'll have available, and it will slow down more. The older a smartphone gets, the more worn the SSD gets, and the slower it becomes. That's why modern Android phones use a utilty called "Trim." It also may help to go with Android 4.3, because that provides Trim support.
Sindar should check out the Lagfix app in the Google Play store. He'll have to root his phone to use it, though.