How is Salva's character changing throughout chapters 1-4

Salva retains hope a bit more easily than Nya. Nevertheless, Salva’s experience is arguably a more perilous one; over the course of his exile from home, he endures starvation, heat exhaustion, dehydration, almost being shot, almost drowning, almost being attacked by crocodiles, and almost being forced to fight. He loses a best friend, his uncle, and, to the best of his knowledge at the time, his entire family. Despite all of this, Salva maintains the will to endure.