I have found the solution by myself.
Thank you anyway.
I have installed Realbox 4.1.0 on a raspberry pi 3 and everything runs as it should. The only thing is, that i cannot get a N64 retro controller to work properly. I have tried a lot of adaptions in the InputAutoCfg.ini file in /mupen64 according to the threads I found online but none of them worked. Everytime I start Super Mario64 on the emunlation the file is resetted to its original content. When I add the line "n64.configfile=dummy" in recalbox.conf it as shown in the tutorials the situation is getting even worse. With this line the y-axis of the controller does not work anymore.
Is there any solution to get a this controller to work? I have bought those:
Thanks a lot in advance.