Now I have changed the Settings.yaml (see below).
Backend Login: Page Not Found
.. but when I add @user-admin to the url (it works).
TYPO3:
TYPO3CR:
contentDimensions:
'language':
label: 'Language'
icon: 'icon-language'
default: 'de'
defaultPreset: 'de'
presets:
'de':
label: 'Deutsch'
values: ['de']
uriSegment: 'de'