How to remove Roca dual flush cover?

Hello! The flush on my toilet (which I suspect to be a Roca PL2 Dual) is not well connected to whatever is behind it and means my toilet has a very weak flush. I think I know how to fix it, but I can’t seem to get this cover off to investigate. When I try and pull it away I am met with resistance. Can anyone let me know how to remove this safely? Thank you

Hello! The flush on my toilet (which I suspect to be a Roca PL2 Dual) is not well connected to whatever is behind it and means my toilet has a very weak flush. I think I know how to fix it, but I can’t seem to get this cover off to investigate. When I try and pull it away I am met with resistance. Can anyone let me know how to remove this safely? Thank you