Complete credits for the French songs can be found on the French 45 rpm of the series:
https://www.bide-et-musique.com/imag...y/EIM-1456.jpg
Japanese credits that are not on the French CD come from Japanese vinyl (JBX-2002).
I don’t know where to find the info about the singer of the German Opening Theme.
It’s written that Karel Svoboda performed the song on the German CD on VGMdb (
https://vgmdb.net/album/31036), but I don’t think that the composer Karel Svoboda is a singer too… Surely it’s just about the instrumentation.