Example Godot-Script file for player movement for me to use for reference.

Player.gd

extends KinematicBody2D

# Declare member variables here. Examples:
# var a = 2
# var b = "text"

const UP = Vector2(0,-1)
const GRAVITY = 20
const MAXFALLSPEED = 200
const MAXSPEED = 80
const JUMPFORCE = 300
const ACCEL = 10

var facing_right = true

var motion = Vector2()
# Called when the node enters the scene tree for the first time.

func _ready():
	pass # Replace with function body.


# Called every frame. 'delta' is the elapsed time since the previous frame.
#func _process(delta):
#	pass
func _physics_process(delta):
	motion.y += GRAVITY
	if motion.y > MAXFALLSPEED:
		motion.y = MAXFALLSPEED
		
	if facing_right:
		$Sprite.scale.x = 1
	else:
		$Sprite.scale.x = -1
		
	motion.x = clamp(motion.x, -MAXSPEED, MAXSPEED)
	
	if Input.is_action_pressed("right"):
		motion.x += ACCEL
		facing_right = true
		$AnimationPlayer.play("Running")
	elif Input.is_action_pressed("left"):
		motion.x += -ACCEL
		facing_right = false
		$AnimationPlayer.play("Running")
	else:
		motion.x = lerp(motion.x,0,0.2)
		$AnimationPlayer.stop()
		
		if is_on_floor():
			if Input.is_action_just_pressed("jump"):
				motion.y = -JUMPFORCE

	motion = move_and_slide(motion, UP)