Below is a list of light bulb types used in 2018- MERCEDES-BENZ A-CLASS lighting system, covering hatchback and saloon 4-door vehicles.
Headlight bulb: low beam - H7 / high beam - H7
Rear indicator/turn signal bulb: PY21W
Back-up light bulb: W16W
Light bulb sizes for other MERCEDES-BENZ A-CLASS generations: A-CLASS (W169) / A-CLASS (W176)