How was love able to transcend the dimensions? And how were THEY (people from future) actually able to communicate?
The main theme of Interstellar is that love transcends the dimensions of space and time. Space means distance. We love a person distant from our location, like a friend studying abroad. With respect to time, we love people who have passed away. We go back in time to love their memories. I don't know if love can move forward in time. Maybe feeling love for expected newborn.
They built a 5 dimensional space based on the relationship of love between Cooper and Murph. They gave each moment a separate room (space) so Cooper can go to whichever moment (time) between him and Murph and try to communicate the means to save humanity.