To extend a given image from a smaller SD card to a larger one is more complicated as I initially thought.
Whenever I copy a older image file to a any card it get always the same size on this card whle the addtional space isn’t used.
When i try to enhance it and reapply the image it is still the same size.
Also using dd doesn’t give a different result.
So I used another image to start the Machine and put the card reader into one usb port.
Here I take a backup using tar and copy it to a network drive. After I use fdisk to drop the second partion and create it again using all space. Now I get back the files from the tar file and replace the SD card.
Now it get boot up showing the addtional size.