battery charge last two days, what can I do to extend battery life

You should charge your Apple Watch every night while you are sleeping, or if doing sleep monitoring, then at another time of the day.

Repeatedly exhausting the battery 🪫 is the FASTEST way to kill a Li-Ion battery.

I’ve had my Series 4 for four+ years and my battery health is at 88%, which is very good for a four year old battery device that is used and charged every day.

To understand Apple Watch performance and its relation to your battery, see:

Apple Watch - Battery - Apple

Apple Watch Battery and Performance - Apple Support

“Battery life” is the amount of time your device runs before it needs to be recharged. “Battery lifespan” is the amount of time your battery lasts until it needs to be replaced. Maximize both and you’ll get the most out of your Apple devices, no matter which ones you own. See the "Tips for Apple Watch" section in:

Batteries - Maximizing Performance - Apple