Hi Jan
There is many thinks that can affect the battery life and it sounds like you have already done a lot of them. I do have some suggestions you can check. A lot of them have to do with the screen:
Turn on Dark Mode: Settings > Personalization > Colors > Choose Dark.
Disable unnecessary apps running in the background: Settings > Apps > Installed apps, and toggle Background app permissions to Never for apps you don’t need running in the background.
Adjust Sleep and Screen Timeout Settings: Settings > System > Power & battery > Screen and sleep.
Disable Unnecessary Startup Programs: Open Task Manager (Ctrl + Shift + Esc), go to Startup tab
Check Battery Usage: In Settings > System > Power & battery, you can see which apps are consuming the most power. Optimize or remove high-usage apps
Hope you can use some of the suggestions above.
Best regards
Thomas