There's a way to make the player push stuff with physics, but chances are you want to have control over your pushing and make it work more like pushing blocks in ocarina of time. There are ways to do that that wouldn't need any of the extra properties of rigid body. But either way, the script doesn't even allow the player to move since you don't have anything like
linear_velocity += motion. Motion is not a property of rigid body, so changing motion does not change player movement. And because of the way rigid body works, you have to change the built in
linear_velocity to move it.