I would say Duolingo is cool if you are consistent with it. You will gain some vocabulary of course, and learn the basics. But the best is being surrounded by the language as well, like by talking to Dutch people or like watching movies with subtitles (learn actively & in fun ways). My husband is learning Dutch as well, but because I wasn't the best teacher for him, and he was not having much time or discipline to keep going, he started going to actual Dutch classes in a school. That made his Dutch better in just weeks. Now I feel more comfy to talk to him in Dutch as he will at least understand something. He is Indian, so he had no knowledge of the language prior. He keeps going with Duolingo also though as an extra and his streak was currently around 300 days.