Complex sentence: Karoline Herfurth was shown the script back in 2000, but she was to young to play Lena so Gansel promised her the role of Nora, but as production was delayed Herfurth became old enough for the part of Lena.
Split into simpler sentences: Karoline Herfurth was shown the script back in 2000, but she was to young to play Lena, so Gansel promised her the role of Nora. But as production was delayed, Herfurth became old enough for the part of Lena.