Hey there, Malgosia2022,
Thanks for stopping by the Apple Support Communities for help with your Apple Watch battery.
The rate at which the battery drains throughout the day is determined by a number of factors, all of which are specific to your charging and usage habits. If the battery is draining faster than you expect it to, we would suggest reviewing the information in Apple Watch Battery and Performance - Apple Support to get started.
Should you still have concerns over your battery life, we would suggest either taking the Apple Watch into an Apple Store or Apple Authorized Service Provider for an in-person inspection, or getting in contact with Apple Support directly. In either instance, whomever you work with will have access to the necessary tools and resources to determine if there's a problem with your battery, and what options you will have moving forward.
To get the location of your nearest Apple Store or Apple Authorized Service Provider, view their contact information, and make a reservation, please visit: Apple - Find Locations
Or, to speak with Apple Support directly to get more information and review your options, please reach out here: Get Support
Cheers!