51 23 131 Adjusting left or right striker on engine compartment lid

Adjusting striker is described in: 

ADJUSTING ENGINE COMPARTMENT LID

Unclip anti-twist lock (1).

Unscrew retaining hook (2).

Installation note: 

ADJUST ENGINE COMPARTMENT LID

Fig 1: Removing Engine Compartment Lid Striker

Courtesy of BMW OF NORTH AMERICA, INC.