To improve the quality of the recording, I bought this microphone from Sennheiser incl. Windbreak. Our expectation has been fully confirmed: the results are above the level of the built-in microphone and lift so that the quality of each recording.
Since the connection to the camera via a 3.5 mm jack, so we are bound not only on this camera, but could also use it to future camcorders, as long as they also have a corresponding input.