Geen of niet?
When do you use "geen" and when do you use "niet" when you talk about things in the negative?
Geen means no. Example: I have NO pen! And niet means not. Example: I do not have a pen! Hope you keep learning and I hope this helps!
Long story short, "geen" almost always comes before nouns, unless "de" or "het" precedes the word. Other than that, "niet" comes before adjectives if that is what is being modified to the negative, and it comes after verbs if they are being modified.
This is a general rule that I like to use, although I'm not sure if it always works.