First and foremost, I am very grateful to Prof. Dr. Valentin Blomer for raising my interest in modular forms, his continuous support during my master and PhD thesis and his valuable feedback. Furthermore, I sincerely thank Prof. Dr. Brüdern for his counsel, constant support and his open-door policy. Moreover, I thank my girlfriend Bri, my office mates Burkhard and Rebecca as well as Max for advice, emotional support and consistent encouragement. Last but not least I would like to thank my parents for their counsel and support.