First you have to remove the fork.
Then take a hammer and hit the red marked ring from above until it comes off.
This ring is not welded, it will come off without cutting something.
After that you can reinstall the fork without this "spacer-ring".
The good thing is, that in this variant...
You don't have to modify your fork. I guess it's easyer to remove the rings. Moreover, you can undo it if you want.
The rings come down easy, if you hit them a few times.
I did it this way and it worked well.