After his release in May 1946, he returned to Bavaria, where he founded his own band and performed in American GI clubs in Füssen and in Landsberg am Lech.
His career was further promoted by the successful record producer Michael Jary and Bertelmann's performances in the first television broadcasts of Nordwestdeutscher Rundfunk (NWDR) in Hamburg from 1952.
[3] It was itself covered in 1986 by the Finnish actor Vesa-Matti Loiri in his role as Jean-Pierre Kusela, whose song "Naurava kulkuri" likewise had success.
Other hits included "Wenn es Nacht wird in Montana", "In Hamburg sind die Nächte lang", "Zwei Gitarren am Meer", "Ein kleines Lied auf allen Wegen", "Arrivederci Roma", "Meine Heimat ist täglich woanders", "Ti amo Marina", "Schwalbenlied", "Es wird in 100 Jahren wieder so ein Frühling sein", "Gitarren klingen leise durch die Nacht", "Es ist ein Herzenswunsch von mir", "Ich wünsch' dir eine schöne Zeit", "Die Mühlen", "Mit dir möchte ich 100 Jahre werden", and "Amore mio".
In Europe he performed together with stars including Marika Rökk Vico Torriani, Hans-Joachim Kulenkampff, and Caterina Valente.