Hi @Zing
Thanks a lot for your information!
I checked the links and I'd say, yes that helps. I switched the emulator in the metadata to MAME2010 / 2015 and then it worked (I think liberto was selected as default and that did not work).
Thanks also to everyone and of course the french developer team for the amazing work. And yes, if there's translation or technical documentation, or maybe programming needed, I'm happy to contribute in the future.
Regards,
fredisback81