Can't access cn=config through Apache Directory Studio GUI

So I answer it by myself, got it now, big confusion and misunderstanding of the dynamic configuration. Maybe someone has the same problem:

There is a difference between olcRootDN in dn: olcDatabase={1}mdb,cn=config and dn: olcDatabase={0}config,cn=config

in my case the olcRootDN in olcDatabase={0}config,cn=config was not set at all. So I added it like explained in the link and also olcRootPW.

Now I can access the cn=config in Apache Directory Studio GUI and edit it comfortable. It is good to have two different Passwords to not accidently delete something in cn=config