How to remove headliner from outer roof shell

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Hello evereyone! I want to convert my hydraulic roof into a manual roof after several issues with the pump and cylinder.
For this conversion I need to know how to remove the headliner of the outer roof shell. So I don't mean the inner headliner, I've already done that.
Does anyone have a clue how this outer headliner is attached to the roof shell? I'd love some advice! Thanks!