Hi Lydia,
I believe there are railcards you can get that allow you to use the train between Gronau and Enschede, lots of students are in the same position as you so it is not uncommon. I don't have any personal experience with that - you could try asking on the Saxion students facebook page?
You can apply for an ISIC for student discounts through their website. Saxion also gives out a student card for identification. You will receive an email when you can collect it from the Saxion building.
I hope that helps a bit,
Sam