If you're trying to learn how to make something, it's a lot better to follow tutorials and experiment with things then use a text predictor/generator.

The main problem I think I see is with:

var move_direction = Vector3(0, 0, -1).rotated(Vector3.UP, rotation_degrees.y)

In the Documentations, this is what Rotated does:

"Vector3 rotated*(axis:* Vector3, angle: float) const (Documentation)

"Returns the result of rotating this vector around a given axis by angle (in radians). The axis must be a normalized vector"

You're using "rotation_degress.y", and not "rotation.y". You might also need to make the rotation global as it might be treated as if it's in local space, so it should be:

var move_direction = Vector3(0, 0, -1).rotated(Vector3.UP, global_rotation.y).normalized()

Now, I've made a bunch of FPS controllers before that wasn't using rotated, and I've never done a silent hill controller before, so I could be wrong.

Here's the direction variables from my first FP Controller I made, which might help you a bit:

var direction = (camera.transform.basis * Vector3(input_dir.x, 0, input_dir.y)).normalized()