The first image shows general view of the hedge trimmer. Note there are hidden screws under the rear handle cover (pink arrow) and under the front handle assembly. These must be levered off and unscrewed/pulled-away respectively. Splitting the casing can be a dirty job, so protect surfaces.

The second image shows the casing split apart after undoing 15 silver screws and 2 black screws (including the hidden screws mentioned above). Also undo the 2 screws securing the mains cable. The whole mechanical and electrical assembly can now be lifted out (maybe a little force required if very old/dirty).

If you're lucky, the motor and its cabling will all be held (by friction) in one of the casing halves as shown, so the casings split cleanly. Either way, for reassembly it's easier to arrange it as shown. Be careful not to loose the 2 springs in the switch activation levers.

Optionally you can separate the motor and its cabling from the heavy cutting blades by undoing the green arrowed screws and then the red arrowed screws (4 off)