It is hard to tell in the picture what is going on and I think we have a communication barrier here. It looks like it is just stripped. Try carefully Dremel-ing a slot in the bolt that is big enough to fit a medium sized flat head screwdriver. That should do the trick.
You can also try a damaged screw remover, it will drill out the bolt a small amount and then it threads itself into the drilled out part in reverse causing the screw to come out. Not sure where you'd get one in Europe.
As posted previously a dremel tool with a small cutoff disk will work aswell, just cut a small slot in the screw and remove it with a flat head screwdriver.