I am wondering where the flight log files are stored. They are not filed on the SD card. Do I have to make some chages to the software and if yes: how?

The P3 saves User Flight Records within the DJI GO App to your local mobile device (iOS/Android). These can be played back with the GO App by going to he Home Screen and selecting the upper right corner, paper plane icon, where you will find your flights. These files are stored on your mobile device -> iOS is within DJI GO/FlightRecords folder; Android is within Device Storage/DJI/dji.pilot/FlightRecord. They are normally referred to as .txt flight logs, but they are require translation into any meaningful information. Several sites will perform this translation/analysis including HealthyDrones.

There are also "black box", Flight Data Recorder logs recorded directly by Main Controller onboard your P3. These are stored to an internal memory card on the MC board. These may be accessed by enabling Flight Data mode under MC Settings/Advanced Setting/Enter flight data mode. You then connect a micro usb cable to the front center of the aircraft just below the Phantom logo nameplate, up above the camera/gimbal. You may then access the MC memory card as a disk and copy the Flight Data .DAT file to your local computer/laptop. These files are binary files and also need a translator to convert the binary data to meaningful data to analyze.

Thanks a  lot. I'm going to have a look.

I'm sorry, but ther are not any flight logs stored. The 'box' is empty, allthough I made several flights today... They seemed not to be recorded... The stupid thing is that I can remember that there were flight records in this list. I thought it better to delete them after viewing. The stupid thing is that eversince no flights have been recorded. The list stays empty. I've got the feeling it has something to do with some kind of option I have to change, but I just can't figure it out...

I've uninstalled the GO app and reinstalled it. problem solved.