Has anyone tried melatonin or serotonin for anything before?

My depression isn’t going away, and even when I’m not just sad I’m like “half-alive.” Trying to sleep at night is the worst and I usually have a break down. Per suggestions I’m considering trying melatonin to help sleep, and serotonin during the day to be happier. Has anyone tried these before for anything, if so what, and how did it work?