it works

scripts/killzone.gd

@@ -0,0 +1,16 @@
+extends Area2D
+
+@onready var timer = $Timer
+
+func _on_body_entered(body:Node2D) -> void:
+	print("dead.")
+	body.get_node("CollisionShape2D").queue_free()
+	Engine.time_scale = 0.5
+	timer.start()
+	
+
+
+func _on_timer_timeout() -> void:
+	print("reloading")
+	Engine.time_scale = 1.0
+	get_tree().reload_current_scene()