I got them out. Welding worked actually better as I expected. Thanks Magnus !
The one I brocke because I did not heated it long enough was the worst one. since it was almost even with the case.
The 3rd nut finally stayed on.
Here some pictures, I'm sure I will not be the last one who will look for this, and I hope it will help others as well.
The one right in the picture is No. 1 the shortest one.
Welding on the nut for the second one
Heating at least for 10 min if you have only a propan torch.
Here are the left overs. the left one is the one I had to weld the gap between the end of the stud and the nut.
I hope this will be helpful.
Happy New Year
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