Apartmentzauber(1963)

Because factory owner's son and womanizer Karl Fischer is constantly avoiding his rich fiancée Almut, his father Waldemar sends the flighty little boy to Italy, where he is supposed to work in his future father-in-law's business and come to his senses. The business is a beach hotel where Karl, booked by the drunken janitor as "Carla", ends up in a triple room where two girls are billeted. Karl finds the woman of his life in the beautiful black-haired Karin.