There have already been a number of posts on this blog about sleep. Use the search bar at the bottom of the home page to find these. Here is another article about how to sleep well. I can’t vouch for what it says about supplements, but the psychological advice seems generally sound. For a full programme for treating insomnia, I can recommend this book [here]. The approach described in the book (CBTi) is also very briefly described in this article [here]. This other article [here] describes the sleep disorder: sleep apnoea. This is a potentially dangerous condition which can be treated.