Below example is an answer format that you should follow.
 
Answer: 
These photos depict a sequence of events in an indoor office. Each photo sequentially illustrates the process of passing through a door. 
 
In the first photo, I capture a scene just before someone opens a glass door. 
 
In the second photo, the door is more open, and the person is stepping into the office. Then, I bumped into that person. 
 
In the third photo, after colliding with the person, I cannot move further. 
 
Overall Description: I collided with a person who was entering the room while opening the door.