Apply classic sudoku rules : Each row, column and 3x3 region must contain the digits 1-9 once.
Furthermore, the same digits can not touch diagonally (can't be a king's move away from each other).
You can use Penpa-edit for solving it on your browser.
Solution code: Row 5, followed by row 7.
Please note: The German version of this page has changed. It is possible that this page does not contain the latest information.