Surfing the net, I found the following notice ( www.emfm.de/ladestationen/):

Charging connection over 12 kW

A charging connection over 12 kW capacity (32A, triphase, red CEE plug) needs permission from your energy supplier.

The "Technische Anschlussbedingungen (TAB)" for this kind of connection contains:
(3) Out of in part 2 defined reasons you need permission for the following devices after a prior assement and approval of the grid operator.:
– Single devices with a nominal capacty of more than 12 kW

The TAB is relevant for most german grid operators.

At ENBW a charging station is seen as a „consistent connection“, that needs to be registered.

This means that charging stations with a higher coverage than 16A, i.e. 3 x 32 A need the approval of the grid operator!

My grid operator is "Bayernwerk". I send a mail to bag-e-mobility@bayernwerk.de and got a positiv response within one day:

Dear Mr. van der Meijden,

we have registerd your charging station, You do not need any more steps for the registration process by your grid operator..

If you have any questions left, please contact us.

Kind regards
...

Super service. So now we are legally on the grid :-)

Update 09/11/2020:

Bayernwerk has put an informationsite online on how to apply for the operation of a charging station for ev's:

https://www.bayernwerk-netz.de/de/energie-anschliessen/stromnetz/ladeeinrichtung.html

It is no more sufficiant to just sent a mail, you now need to fill out an application form.

O tempora, o mores ...