After graduating from the Christian-Dietrich-Grabbe-Gymnasium Detmold in 1999, Westerwelle completed internships in advertising agencies and took courses at the music and art school in the city of Bielefeld in the areas of video, film, photography and fine art. From 2001 to 2006 he studied film/television at the Academy of Media Arts in Cologne, his professors were Jeanine Meerapfel and Matthias Müller. As part of this course, short films were made (Because now the night is coming, Far from Dem, Open to the Top, Think of Us Two) as well as the animated film Simplicity and Complexity is one for the final show of the local Central Saint Martins College of Art and Design during the London Fashion Week.His first feature film, As Long as You Are Here, was invited to the Cinéastes du Présent competition at the Locarno International Film Festival in 2006, where it was particularly mentioned by the jury. The film continued to screen at other festivals around the world and won further awards, including: the Diversity Award and the Grand Prize of the City of Terrassa at the Barcelona Film Festival 2006, the Ottavio Mai Award at the Torino Film Festival 2007 and the Queer Lisboa Award at the Lisbon Film Festival 2007 as well as the Special Gold Prize of the German Short Film Prize 2006 for films over 30 minutes. In 2008, Westerwelle was awarded the North Rhine-Westphalia sponsorship award. In 2012 he produced the documentary Detlef, in which he, together with Jan Rothstein, portrayed the life of the gay rights activist Detlef Stoffel. The documentary was an official entry in the Panorama of the 62nd Berlin International Film Festival in 2012. A year later he presented his feature film Lose Your Head in the same section.In addition to his work as a director, Westerwelle also works as a screenwriter and production designer.