I never had a sleep problem (81 y.o.) as I go to bed already needing to sleep. All I know -- and seems to work for me -- is that even tho I'm retired, I have my days planned to Do What Matters, also called purpose. So one reason I go to bed is to be restful enough next day to be able to do what I need-to and-want to do. Of course that needs that I am in reasonably good health and fitness levels. So while I eat what is nutritious, it's also Delicious Enough. That means being physically active even on days when I'm stuck in my apt, by devising ways to exert enough to be in reasonably Optimal shape. Bad food choices, not managing stress well and inactivity results in poor sleep.
There is good advice on most top universities and federal and provincial websites -- these people don't profit out of their advice therefore trustworthy.