I love to come to Fotografiska not only for the great exhibitions that they are having and that are changing frequently, but also for the restaurant which you will find on the top floor. Here you have panoramic views over the city and can enjoy a really nice dinner! You can also just get a drink after your museum visit there.
Pro tip if you plan to come here more often during the year: become a member and get a monthly pass (6 months cancellation time).