Step 4 is wrong.
You cannot pull the battery out on bottom edge because of the grey plastic arresting aids which you can see in the picture of step 3.
You first have to slide the battery as far as possible to the bottom edge into these grey parts so that the plug connection on top gets lose slightly and then carefully pull it out on side of the mainboard connector.

Also you do not need that Jimmy in step 2. After removing the screws just pull and lift the base cover with your fingers from the area where the hinges are located and then it easily slips out at the front.