Fehler im Backend

Hallo Community,

ich habe da ein Anliegen und zwar habe ich Drupal 7 installiert und ein neues Theme aktivert, erhalte aber im Backend diese Fehlermeldungen.

Notice: Undefined index: bartik in drupal_theme_initialize() (line 100 of /www/htdocs/w0104720/includes/theme.inc).
Notice: Trying to get property of non-object in _drupal_theme_initialize() (line 146 of /www/htdocs/w0104720/includes/theme.inc).
Notice: Trying to get property of non-object in _theme_load_registry() (line 335 of /www/htdocs/w0104720/includes/theme.inc).
Notice: Trying to get property of non-object in _theme_load_registry() (line 319 of /www/htdocs/w0104720/includes/theme.inc).
Notice: Trying to get property of non-object in _theme_build_registry() (line 713 of /www/htdocs/w0104720/includes/theme.inc).
Notice: Trying to get property of non-object in _theme_build_registry() (line 713 of /www/htdocs/w0104720/includes/theme.inc).
Notice: Trying to get property of non-object in _theme_build_registry() (line 713 of /www/htdocs/w0104720/includes/theme.inc).
Notice: Trying to get property of non-object in _theme_save_registry() (line 343 of /www/htdocs/w0104720/includes/theme.inc).
Notice: Undefined index: bartik in theme_get_setting() (line 1431 of /www/htdocs/w0104720/includes/theme.inc).
Notice: Trying to get property of non-object in theme_get_setting() (line 1468 of /www/htdocs/w0104720/includes/theme.inc).
Notice: Trying to get property of non-object in theme_get_setting() (line 1478 of /www/htdocs/w0104720/includes/theme.inc).

Ich komme auch nicht ins Frontend. Das Frontend wird doch direkt auf der Startseite angezeigt, also domain.tld oder?

Meine Domain ist http://internetblogger.name.

Kann mir jemand helfen? Ich würde so gerne Drupal nutzen.

Danke im Vorfeld!