de / het
Many nouns are introduced without using a definite article, so the learner does not know, whether it is a de-word or a het-word. The rules for deciding "de" or "het" are complicated and have a lot of exceptions. Of course, as a native German speaker I can't complain, but I think it would be very helpful, if the "de " or "het" were always shown, in the overview of the lessons and in the translation of the words in the single questions as well.
Small hint for deciding wether it's de or het:
If the German word uses 'das' it's usually 'het'
If the German word uses 'der' or 'die' it's 'de' in many cases.
But yes, for learners who aren't used to multiple definite articles it might be handy.
If you speak and you don't know, you can always make the word 'smaller'. In that case it is always 'het'. De muis, het muisje (the mouse, the little mouse or actually it would be something like ´the mousey´). It's a tric you can use if you want to use the right def art.
It's a good idea. Something I usually do when in trouble with eng-to-nl translation exercises is to hover my mouse over the definite article: the first dutch article shown in the hint list is always the right one.
If you want, there is a whole website (and app) to help you with this: https://www.welklidwoord.nl/. You enter the word, it tells you the article. Easy-peasy!