Problem with pwndbg


I am trying to write an exploit for Dovecot (CVE-2019-11500). I downloaded an older version of Dovecot and got it to work (I just did the basics). Now I wanted to debug the program with pwndbg to inspect the heap but there was a failure:

pwndbg> r Starting program: /usr/local/sbin/dovecot process 6484 is executing new program: /usr/local/bin/doveconf process 6484 is executing new program: /usr/local/sbin/dovecot [New process 6488] [New process 6489] process 6489 is executing new program: /usr/local/libexec/dovecot/anvil [tcsetpgrp failed in terminal_inferior: Kein passender Prozess gefunden] 

(Kein passender Prozess gefunden translates to No appropriate process found)

I am pretty new to whole heap exploit and gdb thing so could somebody help?