First I added a figure model to the scene to compare the size of the corridor and the door, then used the Insert Loop Edge tool to determine the position of the door
Then delete the face for the door and use the extrude tool to create the load-bearing wall and add a bevel modifier to it
Then use the mirror modifier to create the opposite side of the wall
Use the Extrude and Bevel tool to create the baseboard and then add Shade Smooth to it
Then mirror the ground along the x-axis using the Mirror modifier and add the ground
Create the ceiling and door by using Extrude, Insert and Bevel
Use the same method to create the frame for the door
Then create the alarm and siren
After making the windows, the basic scene is complete