Complex sentence: He won gold at the national allround championships in Heerenveen, at the European allround championships in Heerenveen Kramer, and at the world allround championships in Hamar.
Split into simpler sentences: He won gold at the national allround championships in Heerenveen and at the European allround championships in Heerenveen. Kramer won gold at the world allround championships in Hamar.