Insomnia is difficulty getting to sleep or staying asleep for long enough to feel refreshed the next morning.
Causes, self-tips and Treatment can all be accessed here.

https://www.nhsinform.scot/illnesses-and-conditions/mental-health/insomnia/

 Sleepio - 6 week course for insomnia and sleep disorders (smartphone app) - https://www.sleepio.com