@Sempf check out "Cracking the Cryptic" on YouTube and get into variant Sudoku if you want to burn *many* hours. Marty Sears' Rat Run series is a great place to start if you're already comfortable solving normal Sudoku:

https://logic-masters.de/Raetselportal/Raetsel/zeigen.php?chlang=en&id=000IFI