Traduction de l’étape 1
The button has a little prong in the middle that has a recess, and two hooked prongs, that release when turned counter clockwise.
To release it, be careful to avoid the extra ring you see around the button. That is part of the sealing assembly.
Lift the button carefully with very thin flat screwdriver, or dentist tools, and pry it off while rotating counterclockwise. This shoudl be the result.