1. The comics by Rob-Vel (creator of Spirou) are collected in french in this book : Spirou par Rob-Vel :

Two short stories by Rob-Vel are also in nr. 3 in the 'hors-série' (outside-series) of Spirou : La voix sans Maître :

Most of the comics in Spirou par Rob-Vel have been published in German in the Spirou Spezial albums 13 to 18 (I think all of them except for 1938 Spirou 1 by Rob-Vel and Cauvin in 1970). The format is a little different, though: the French book, unlike the German albums, doesn't include the Journal de Spirou masthead (magazine title) on each page.

The cover of "Am anderen Ende Angst" suggest a scene from nr. 43. Vito la déveine (in French) / nr. 41. Vito Der Pechvogel (in german).
But that cannot be the right answer.

Internet tells me Nr. 0 contains different short stories from different artists.
'Am anderen Ende Angst" Is probably "La peur au bout du fil" par Franquin.

An other story in Nr. 0. is "Eine Stimme versagt den Dienst"which is most likely in french : "La voix sans maître" by Tome and Janry. (see the nr. 3 of 'hors-série above)

Spirou 0 was created especially for Germany by collecting different short stories (see content here). In French, they are spread across different collections, mostly the four – soon to be five – hors-série albums (what you might call "Sonderbände" in German):

• "Eine Stimme versagt den Dienst" (La voix sans maître) by Tome & Janry: hors-série (HS) 3
• "Überraschung, Papa!" (Joyeuses Pâques, Papa!) by Fournier: HS 4
• "Die Geheimnisse der Tiefe" (Back to the Rédak) by Yoann & Vehlmann: HS 5 (coming this fall)
• "Am anderen Ende Angst" (La peur au bout du fil) by Franquin: in Spirou et Fantasio 13 Le voyageur du mésozoïque (the German album "Ein eisgekühlter Gast taut auf", previously under the title "Des Wahnsinns fette Beute")
• "Das Sparschwein ruft" (La tirelire est là) by Tome & Janry: HS 3
• "Das Verhängnis!" (La menace) by Tome & Janry: HS 3
• "Der Hummer" (Le homard) by Franquin: HS 2
• "Eine Woche mit Spirou und Fantasio" (Une semaine de Spirou et Fantasio) by Tome & Janry: HS 3