What can you advise to speed up the 3D modeling process?

Question

3D

I model building and exterior models in autodesk 3ds max. My goal is to model a small area of ​​our city with all the buildings and objects. But modeling takes a lot of time. 1 complex building, with modeling, took 1 month to make. How can you speed up the modeling process? Or models do it slowly, or am I doing something wrong? Please write your tips to speed up the process.