Complex sentence: The project was originally developed by character animator Jeffrey J. Varab and animation-expert Jakob Stegelmann, who had established an animation-school in Copenhagen and trained most of the animators who would eventually work on the film.
Split into simpler sentences: The project was originally developed by character animator's Jeffrey J. Varab and Jakob Stegelmann. They had previously established an animation-school in Copenhagen and trained most of the animators who would eventually work on the film.