Many thanks for the answer.
With the "load-button" I have only the possibility to access the files stored in mixpad and cremtet with mixpad How do I open a file that was not created with mixpad and that is located elsewhere in the file system of the device? I am looking for the function "Open File on device" as it is in wavepad, which has access to all files. With the "load button" I can not open any other created sound, or did i miss something here. How should I proceed if I have made a recording with Wavpad and want to mix them in mixPad with other sounds?