I know insomnia. When the nights get to like 20C in summer it just gets worse
Thankfully winter now but still always have trouble sleeping. I have medication now that helps me sleep but before that it would take me 2-4 hours to get to sleep every night, sometimes more. Now I get to sleep usually within 2 hours.
Are you doing anything creative, like writing? Do something like that, then on about the last hour or two before bed watch a documentary on youtube or something. Don't watch stuff you will get to mentally engaged in. Just before going to bed write a small list of things you want to do the next day.
Or you could exercise every day, that helps