I have been trying to use a player movement script from this video:
and I have converted everything to work in Godot 4 to the best of my ability but I'm just a bit stuck with the final one which uses move_and_slide

extends CharacterBody2D

const UP_DIRECTION := Vector2.UP

@export var speed = 600.0
@export var jump_strength = 1500.0
@export var maximum_jumps = 2
@export var double_jump_strength = 1200.0
@export var gravity = 4500.0

var _jumps_made := 0
var _velocity := Vector2.ZERO

func _physics_process(delta: float) -> void:
	var _horizontal_direction = (
		Input.get_action_strength("move_right")
		- Input.get_action_strength("move_left")
	)
	_velocity.x = _horizontal_direction * speed
	_velocity.y += gravity * delta
	var is_falling := _velocity.y > 0.0 and not is_on_floor()
	var is_jumping := Input.is_action_just_pressed("jump") and is_on_floor()
	var is_double_jumping := Input.is_action_just_pressed("jump") and is_falling
	var is_jump_cancelled := Input.is_action_just_released("jump") and _velocity.y < 0.0
	var is_idling := is_on_floor() and is_zero_approx(_velocity.x)
	var is_running := is_on_floor() and not is_zero_approx(_velocity.x)
	if is_jumping:
		_jumps_made += 1
		_velocity.y = -jump_strength
	elif is_double_jumping:
		_jumps_made += 1
		if _jumps_made <= maximum_jumps:
			_velocity.y = -double_jump_strength
		elif is_jump_cancelled:
			_velocity.y = 0.0
		elif is_idling or is_running:
			_jumps_made = 0
		
	_velocity = move_and_slide(_velocity, UP_DIRECTION)

I keep on getting the error Too many arguments for "move_and_slide()" call. Expected at most 0 but received 2. and I have no clue what I have done wrong, and what to do. I would appreciate any help.

    You should check the Godot documentation. Lots of functions have changed.

    You don't need a "_velocity" variable, the CharacterBody2D has a built-in velocity.
    move_and_slide does not return any value and you don't need any arguments.

    Your code should be like this:

    extends CharacterBody2D

@export var speed = 600.0
@export var jump_strength = 1500.0
@export var maximum_jumps = 2
@export var double_jump_strength = 1200.0
@export var gravity = 4500.0

var _jumps_made := 0

func _physics_process(delta: float) -> void:
	var _horizontal_direction = (
		Input.get_action_strength("move_right")
		- Input.get_action_strength("move_left")
	)
	velocity.x = _horizontal_direction * speed
	velocity.y += gravity * delta
	var is_falling := _velocity.y > 0.0 and not is_on_floor()
	var is_jumping := Input.is_action_just_pressed("jump") and is_on_floor()
	var is_double_jumping := Input.is_action_just_pressed("jump") and is_falling
	var is_jump_cancelled := Input.is_action_just_released("jump") and _velocity.y < 0.0
	var is_idling := is_on_floor() and is_zero_approx(_velocity.x)
	var is_running := is_on_floor() and not is_zero_approx(_velocity.x)
	if is_jumping:
		_jumps_made += 1
		velocity.y = -jump_strength
	elif is_double_jumping:
		_jumps_made += 1
		if _jumps_made <= maximum_jumps:
			velocity.y = -double_jump_strength
		elif is_jump_cancelled:
			velocity.y = 0.0
		elif is_idling or is_running:
			_jumps_made = 0
		
	move_and_slide()

    chi11_

    In Godot 4.0, the move_and_slide function does not need any parameter (or more precisely any arguments as variables). In other words, in your this line: velocity = move_and_slide(velocity, UP_DIRECTION), anything cannot exist within the brackets (in your case its: _velocity and UP_DIRECTION). It needs to be remained empty.