You can use the signals: on_Area2D_body_entered()
and on_Area2D_body_exited()
func _on_Area2D_body_entered(body):
if body.is_in_group("Enemy9"):
Enemy9_count + = 1
if body.is_in_group("Enemy5"):
Enemy5_count + = 1
func _on_Area2D_body_exited(body):
if body.is_in_group("Enemy9"):
Enemy9_count - = 1
if body.is_in_group("Enemy5"):
Enemy5_count - = 1