I found out, why the modul was not detected by my Phone.
When i downloaded the example BGLib_stub_slave I installed the libraries in my Arduino IDE. But without opening the libraries localy it brought up errors while compiling.
After some tries i found out that the BLE can be detected if only the local libraries (all 3: BGLib.cpp, BGLib.h, BGLibConfig.h) are in the projectfoldersand the installed ones are deleted (in C:\Program Files (x86)\Arduino\libraries).
I don't know if this is probably normal, but that was my mistake.