Yabba,
Try
www.ns.nl. change the text to English (how nice of them) and just type in from Amsterdam to Kaldenkirchen and the desired time. You get a good schedule. I would say that you could easily be at GT until 20:00 or thereabouts, giving 8 hours to enjoy the garden, sauna, pool and other facilities. Oh, and maybe some girls too.... That should really be sufficient for a newcomer, nein ?
have fun - and report to us when done ;-)
Gaston