Switching to natural means
cannot be fast, but unless you have an underlying physical problem it's
definitely possible.
The first issue that cannot be ignored is that coffee, alcohol, other intoxicants, prescription sleeping pills etc mess with your body's natural rhythms. Ditto things like playing on-screen games that pump in adrenaline, and keep you focused and awake "all night".
(edit: added coffee. Thanks Rodafina)
Second: you have to sleep and wake at approximately the same time almost every day.
You can break this rule say once a week when you're young, and one every ten days when you're middle-aged, but if you break it too often it will mess up your sleep cycle.
Ditto travelling between time zones in the "wrong" direction interferes. You have to
work on recovery when you get back.
Third: Your body
needs adequate food, sleep, and exercise. (they're not first on the list OFC - that starts with oxygen, temperature control, water for hydration - but they're the ones that matter here).
If you want to manage your body rhythms, you need enough of those three.
* A walk every day is enough exercise for this objective. More is good, and exhaustion is a better way to force sleep than pills, but 30-60 minutes walking is adequate.
* You can't operate long-term on carbs, sugar, and fat (junk food), but you don't need the latest "superfood diet for everlasting life" either
"Normal food", slow-release carbs only, manage fat (less damaging than sugar by far, but too much can be an issue), eat more low-starch veg.
NB: you don't have to sleep 8
continuous hours to be healthy. You have get
enough "good sleep" Split-sleeping is fine if it works for you.
What hurts is long periods of too little sleep, or low quality sleep - that will take years off your life (really: that's not hyperbole).
Last point: After removing all the negative factors, you can shift the time(s) you fall asleep up to maybe 60 minutes a day. Big steps don't normally work. But there's no rush. From any given stable starting point, just wake up a little earlier (maybe 30 min) every few days and then get up and
do something to bring your body up to "normal operating conditions" (morning walk is good).