This thesis represents more than just an academic achievement. It marks a new chapter in my life, one that has been filled with lots of fun, fulfillment, and rewards that will endure for a lifetime. I would like to sincerely thank everyone who has supported me along the way.First and foremost, I thank my supervisors: Gertjan, Gosse, and Arianna.Gertjan, you were a constant source of support that I needed many times. As my supervisor, you always made me feel secure and confident, not only in my academic pursuits but also as a person. Your guidance on my research direction has played a pivotal role in this thesis. I will also always remember our attempt at a 40 km walk, even though I was not unable to finish it.Gosse, in addition to your continuous mentorship for my research and this thesis, your calm attitude and patience as a supervisor, were perfect examples for me to follow, especially as an ambitious and sometimes impatient student, that helped me become a better researcher. I also genuinely enjoyed our lunchtime chats, particularly about cycling, which made me excited to watch the Tour de France at the end of 4 years.Arianna, I'm very glad that I asked you to be my supervisor when you joined the department. Your knowledge and guidance in my research interests, your attention to precise details and pursuit for "excellence" have deeply influenced this thesis and my perspective on research. I also never imagined having a supervisor with whom I can speak Turkish which is an unexpected delight, especially with your kids. I believe we made a great team, and working together was a truly enjoyable experience. Once again, I thank my supervisors.Throughout my PhD, I had the opportunity to collaborate with a group of exceptional individuals. I would like to thank Asa Cooper Stickland, Alexandre Berard, Barbara Plank, Matthias Gallé, Rob van der Goot, Laurent Besacier, and Sebastian Ruder for their invaluable contribution to my research.I would also like to thank the members of my reading committee, Joakim Nivre, Jörg Tiedemann, and Jack Hoeksema, for reading my thesis and providing me with useful feedback which helped to improve this thesis.