Complex sentence: Piemur has doubts about his future in the Harper Hall, unsure of what will become of him when his voice breaks, and shares these doubts with Menolly, who convinces him to concentrate more on the present.
Split into simpler sentences: Piemur has doubts about his future in the Harper Hall, unsure what will become of him when his voice breaks. He shares these doubts with Menolly, who convinces him to concentrate more on the present.