Also, sometimes a factory rest after a major update can help, but I would wait on that until the 3.1 comes out first. This Android 11 is a really buggy update for a lot with screen rotation failing and sensors randomly stop working.
Its been a disastrous update from my experience.
First of all determine if an app is causing the battery drain. Open Device Care, click on Battery, click on the graph. It will show you how much battery each app has used. You can look at it from last full charge or last 7 days. If an app is using more battery than you expected, stop or remove that app.