The short answer

The hard part of Dutch is not the grammar, which is close enough to English to come quickly. It is the vowels, which include three or four English simply does not have, and the fact that nobody in the Netherlands will let you practise, because they switch to English out of politeness the moment you slow down. This is somewhere to be slow without anybody rescuing you. The tutor hears your audio rather than a transcript, so the ui and the guttural g are things it can actually work on with you.

Dutch is a strange one to learn, and the difficulty is social as much as linguistic.

The grammar is genuinely approachable for an English speaker. Word order takes adjusting, the verb goes second, and separable verbs will annoy you, but there is no case system to memorise and a great deal of vocabulary is recognisable on sight.

The sounds are another matter, and the practice environment is hostile in an unusually polite way.

Nobody will let you practise

Ask a question in Dutch in Amsterdam, hesitate for a second, and you will be answered in fluent English. This is meant generously and it is completely sincere, and it makes the country one of the hardest places in Europe to actually learn its language.

The result is that Dutch learners get very little production practice and a great deal of passive exposure, which produces people who understand a lot and speak almost none.

An app that will talk to you for thirty minutes without ever switching to English is a genuinely useful thing to have here, and it is most of why people learning Dutch end up wanting one.

The vowels are the work

Dutch has at least three vowels with no English equivalent: ui, eu and uu. There is no English word to point at for any of them, which is why written explanations do so badly and why hearing them repeatedly matters more.

Your audio goes to the model directly rather than being transcribed first, so the tutor is responding to the sound you made rather than to a text version of it. If you approximate ui with something closer to ow, a transcript will frequently give the tutor the word you meant. Speaking to something that hears the vowel is the only way that gets corrected.

What a session is

Unscripted conversation, with something you can interrupt, that will not graciously switch to English. Behind it sits an authored CEFR syllabus of 294 items from A1.1 to C1, of which 106 are capabilities: concrete things you can do. What you keep getting wrong shapes later sessions with nothing to configure.

The tutor roster includes Ghent, so you get Flemish alongside the Randstad. The two differ enough in vowel quality and in the softness of the g that it is worth hearing both early.

Going to the Netherlands or Belgium

Travel Mode changes the app for the length of a trip: rehearsal before you go, one real-world mission a day while you are there set in the city you are in, and a debrief with your tutor afterwards about how it actually went.

For Dutch specifically, the missions are worth more than usual, because the hardest part is not knowing what to say. It is holding your nerve for the three seconds it takes somebody to decide whether to switch to English.

The five Dutch tutors

Every language has five, each from a different place and each sounding like it. You can switch whenever you like, and the app remembers where you are regardless of who you talk to.

SanneAmsterdam
Clear, standard Randstad Dutch with the lively, slightly nasal colour of the city.
BramRotterdam
Standard Dutch delivered with the practical, no-nonsense rhythm of the harbour city.
LiekeUtrecht
Clear, refined standard Dutch with a softly upbeat intonation.
DaanThe Hague
Polished, slightly formal Randstad Dutch with the buttoned-up poise of the government city.
JorenGhent
Soft, melodic Flemish Belgian Dutch with gentler vowels and a warm southern lilt.

What English speakers usually find hard

These are drawn from the pronunciation patterns the tutor listens for in Dutch. Because it hears your voice rather than a transcript of it, they are things it can actually notice and work on with you.

ui, the vowel with no English equivalent at all: The signature hard Dutch sound. A front-rounded diphthong: start with an uh with the lips rounded and glide toward a y. Huis, tuin, buiten, uit. It is not ow, not oy, not oo, and there is no English word to point at. Most learners approximate for years.
The g, and how far south you are: A scrapey fricative made at the back of the throat, harder than the ch in Scottish loch. In the Randstad it rasps; in the south and in Flanders it softens considerably. Combined with sch, which is that sound plus an s, you get Scheveningen, which was used as a wartime shibboleth for exactly this reason.
eu and uu, borrowed from French and German: Two more front-rounded vowels English lacks. Eu is the vowel of French deux: neus, deur, leuk. Uu is the vowel of French u: nu, vuur, minuut. Both need rounded lips with the tongue forward, which feels wrong until it does not.
ij and ei sound identical, and you just have to know which: Mijn and klein use the same vowel. Only the spelling differs, and it is learned word by word. Similarly ou and au are one sound, while oe is a plain oo, so boek and bouw are nothing alike despite looking similar.
Final consonants devoice, and final n disappears: Heb sounds like hep, hond like hont, dag like dach. Meanwhile the very common -en ending usually loses its n in speech, so lopen is lope and mensen is mense. Between the two, spoken Dutch is noticeably shorter than written Dutch.