After seven years of doing five/ten minutes a day I've come to the end of Duolingo's Dutch lessons.
Congratulations, or should I say Gefeliciteerd!
Bon chance!
Speaking Dutch and French you'll be applying for a Belgian passport next!
Ironically, I've just let my Duolingo sub expire (still do it every day, though). One of the most useful parts, the forum, has been dropped (in Spanish at least) and since Duo gives practically zero grammar explanations the forum was very useful.
On top of that, its Spanish is geared to the Americas so is slightly less useful.
I still say it's a great tool for starting off by virtue of it always being "on me" and the short, snappy nature of the lessons combining to make it easy to give it a go. Less mentally off-putting than digging out that grammar book and doing some exercises.
For learning/reinforcing new vocab I suggest something like Quizlet, a flashcard based app & website. A simple, 2 column spreadsheet file can be copied & pasted in. Vocab can be tested, new language to English or vice versa, visually or spoken. Really great to go for a walk and be practising vocab. I use it also for longer, complicated sentences.
You can also search for what others have created and use theirs!
The likes of ChatGPT can also "converse" in different languages, again written, spoken or both. Very useful for people working on their own.