Le Grand Amour
Pierre married Florence, the only daughter of a small industrialist. 15 years later, he is the boss, but his middle-class life worries him a lot. When a new young and lovely secretary comes, he starts dreaming.
Starring Pierre Étaix, Annie Fratellini, Nicole Calfan, Alain Janey, Ketty France, Louis Maïss, Jacqueline Rouillard
Watch "Le Grand Amour" from streaming services Criterion Channel, Kanopy released in 1969. It's a comedy and romance movie, and has a rating of 7.5 out of 10 from Imdb which is usually fine for this kind of movie.