Managed to solve it. But for reference if anyone else gets stuck:
I just used a heatgun on it for a bit, and the grey stuff got goey. And then I could wiggle it off without any issues. When I assemble the front bumper, I assume I can just heat up the grey stuff again, and reuse that.
Hello!
Currently dissasembling my front bumper for paint.
However I'm a bit stuck on removing the "front bumper side retainer". The workshop manual says "Disengage the welded connections". But I'm unsure what the correct method for doing this is. And how to "reweld" when I get the bumper back...