So, a quick update what I did to improve my battery life. First of all I applied the suggestions from post #2.
I also deactivated all apps from Google I don't use (like the books, games stuff).
I'm switching off WiFi via Automate (no need to discuss this - I know that this will not save humongous battery life) using 'Location based WiFi toggler'.
This is what I did. Based on my usage profile the battery will last for 1-1.5 days.
Sounds like common settings to me nothing special really