Hello Anja...thank you for this outfit. i have been trying to figure out how best to pull off a long dress and flats for work. the long dresses i own are mostly meant to be worn with flip flops at the beach but i am longing for some pretty ones to wear to work to break up the pants rut i am in. and the air conditioning makes it painful to wear anything short...but finding the right flats that don't look awkward with the long length is the key. Your strappy black flats seem to fit the bill perfectly and you have pulled off the look without look swallowed by the whole outfit...my friend stacie paired a long dress with some beat up doc martens (hello 1994 again!) and that really worked as well...gave a rugged look to a feminine shape, which is my favorite combination of styles. i will have to keep my eyes open for some good long dresses that can't be described as maxi or beachy and i think the key is to stay in a darker color palette.
PS. You and your boyfriend are waaaaaaaay too good looking to be dating each other. Puts the rest of us to shame!