Well that brought me a little closer to the solution: the plugin page is empty
Although I am pretty sure the plugin page was not empty before, because I had to activate Imagemagick just after the install.
After a search in the forum on the empty plugin page I can see several answers.
As I am totally new to gallery so I think this is a way of getting to know the product gallery2 better. I will try and solve this myself first.
Thanks