After updating Blender from 2.79 to 2.81, all my bones don't work as they should So all my models are the same. When I try to rotate a bone in pose mode, the mesh kinda rotates faster than the bone. But if I make a new object using the same armature and weight paint it and all that, it works fine.

Here's a video of what happens https://youtu.be/kfsslGc6mSg, and the Christmas hat is a new object.
Delete the Rigid Body simulation.



It is good to Apply Object Transform



and parent the character to the armature,



so it will follow it.



I recommend you to transfer the character to the new blend file to get rid of the legacy scene settings.