Going further back into the car, extrude the green edges as shown by the arrows. Don't forget to do some vertex tweaking.
Make the cuts shown in green and weld any overlapping vertices. Select the red edge and extrude it to the center of the car and, again, weld any overlapping vertices.
Select the edges shown in green and make two extrusions in the direction of the red arrows.
Cut in the green edges from the front to the back of the car. You can use "QuickSlice" to speed things up if you want.
Rearrange vertices a little and then select the red polys and extrude them upwards.
Make the cuts shown in green. Adjust vertices to get a nice rounded shape. This hump is the divider for the rear seat area. If you look at your reference images you will see what it looks like.
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Select the green polys and extrude them three times as shown.