How to replace turn signal bulb for Audi A4 (B8)

Automotive turn signals or flashers are flashing lights, located at the front and rear corners of the body. The appearance of these lights are controlled by the driver to tell other road users, that the vehicle is about to end constant movement and start a maneuver. It's very important to exploit turn signals opportunely, thus alerting others about planned actions on a driven vehicle. For the same reason, all turn signal lights have to be in a fully working condition. Commonly, the origin of an unproductive turn indicator is an exhausted bulb, that can easily be discovered while driving: when failing side turn signal is activated, the flashing rate of a relative indicator in the dashboard will be increased, if any bulb has died on a particular side.