Something I didn't know about Groningen before I arrived, was the popularity of thrift/second-hand stores. In England, we often see small charity or vintage shops or markets, but never whole stores at the same scale as the ones that exist here. Mamamini and GoudGoed are two major chains of thrift stores in The Netherlands, with multiple stores across places such as Groningen, Winschoten, Winsum and Uithuizen.
What's really great about thrift shopping in The Netherlands is that by buying second-hand clothes and household objects is that you're avoiding supporting mass-production and fast-fashion. Not only this, it's much more economical for your own wallet, and you're guaranteed to have a one-off item that you'll never see anybody else where! I was often a second-hand shopper before, but since coming to The Netherlands, I love it even more.
Even if you don't buy anything at the store, it's fun to just look around at all the weird and wonderful items. Some, you need to ask yourself; why would I ever need this?
But you can also find some really great stuff for a really good price. Before buying anything new, I'd always check Mamamini or GoudGoed now.