Before start building the scene, I looked for more references of the scene.
To save the time, we decieded to build the roofs and the body of the buildings seperately.
I am responsible for the roofs, here are some working processes.
This is the base shape of the roof, I shared this with Shuang, so she could know how big the body of the building would be.
I devided the roof into four, so I could just model one fourth of them, then duplicate.
Use soft selection to move the corner of the roof up a bit.
Convert polygon edges to curves and extrude them.
Then wedge the faces
Then add some details to the roof edges, I found some references here
Select the roof edges and extrude them once, then turn the “Keep Faces Together” off, extrude them several times.
Which may finally looks lik this
Select the base shape of the roof and extrude some thickness
Duplicate the model