It's a postcard from Hauptmann (Captain) Haupt in Hann. Münden (near Göttingen), to Lore Haupt (presumably his wife). Written on 5-18-1942
Main body transcription:
"XXX!
Nun verlässt uns auch Hptm. XXXX auf ein Kommando. Zu diesem Behufe haben wir uns zu einem vorläufigem Abschieds-Doppelkopf versammelt und grüßen dich herzlichst.
Dein Vati"
rough translation:
"Now Hauptmann (Captain) XXX is leaving us for a command as well. For this purpose, we gathered for a preliminary farewell-Doppelkopf (a German card game) and are sending you our kind regards
Yours
Vati"
Followed by a few greetings by some other soldiers. The exact names are hard to decipher from me, this kind of writing system (Deutsche Kurrentschrift) was stopped being taught in schools in 1941