You have a lovely space and a great context. In this proposal I worked with two main concepts; one is to use "spaces" rather than "rooms" as much as I could, which is the best solutions for small spaces. two is the use of the height of the apartment to create a "Mezzanine floor", this concept was treated very carefully so it can pass the building codes while allowing you to have the best use of your apartment.
I wish you best of luck with your home makeover.
P.S: I have attached a 3d render view for your apartment to give you with a better idea about the proposal.