Dutch Railways (NS) operates a train from Amsterdam Airport (AMS) to Gronau hourly. Tickets cost $27 - $50 and the journey takes 2 h 8 min.
How to get from Amsterdam Airport (AMS) to Gronau
From Schiphol (Airport) train to Enschede then train to Gronau(Westf). 2 h 33 min 47€. From Amsterdam Airport (AMS) drive to Gronau. 1 h 44 min 27€. From Amsterdam airport fly to Dusseldorf airport, train to Düsseldorf Hbf, train to Essen Hbf, then train to Gronau. 3 h 11 min 128€.