Complex sentence: Carla made a good start to the year, reaching the semifinals at Brisbane, losing to Angelique Kerber, and the quarterfinals of the Australian Open, losing to Agnieszka Radwańska.
Split into simpler sentences: Carla made a good start to the year. She made the semifinals at Brisbane, losing to Angelique Kerber, and the quarterfinals of the Australian Open, losing to Agnieszka Radwańska.