Brakes: Two independently acting braking devices.
Bell / horn: For dispensing acoustic warning.
Lighting: Non-blinking front headlamp to illuminate the road of white or pale yellow color. A red rear taillight that stays lit when stationary. [see § 67 StVZO in German.]
Reflectors: front with a white with a red rear reflectors that may be connected to the lights and/or connected to the pedals. At least two yellow reflectors on each wheel.
In daylight and good visibility bicycles may be used without lights.
Racing bike exceptions: Racing bikes are not required to meet the above rules. However, if riding at night, all bikes, including racing bikes are required to have lights and reflectors.
A Racing bike is defined as less than 12 kg, with drop handlebars, a rim diameter at least 630 mm diameter, and a rim width not more than 23 mm. Mountain bikes are not road bikes so are exempted from certain requirements (unless ridden at night on the roads). [NOTE: I do not know if they are exempt from the equipment list if they are ridden on the roads during the daytime.