Although the bottom case is now loosened, you cannot take it off the camera because it is held in place by a lug to the front case.

Removing the front cover completely is unnecessary, especially since it makes reassembly more difficult (the closing mechanism of the camera back likes to go to pieces and the position of the single parts of it is logically difficult to reconstruct).

Therefore it should be sufficient to loosen the front cover just slightly. Refer to Figure 3, and remove screws 1 and 4, while loosen, but do not remove screws 2 and 3. Keep these screws separate from the previous ones, because they have different sizes!