Does it often take a long time for you to fall asleep at night, and is this considered normal development?

Patient's question:

Born in October, currently 132cm tall, weighing 25kg.
Detailed medical condition and consultation purpose: He doesn't sleep during the day and often struggles to fall asleep at night for long periods. Is there a medical issue? Is his development normal for his age?
Current general condition: Normal
Medical history: None

Doctor's answer:

The child may have sleep disorders.