Got it for a (I think) steal around 400€ for the 45mm GPS.
Actually also got a question. How can I use the sleep function for naps? Because I slept more than that. Anyways this is cool!
The two obvious ones are more physical activity, less stress.
Intermittent fasting might give you good results for increased deep sleep. Try eating in a smaller timewindow -- e.g. stop eating ~5 hours before you go to sleep, and have breakfast later in the day.