At first I put Niet goed but because I remembered niet coming at the end in another question, I changed it to goed niet and it was wrong. How do know whether to put niet before or after?
Usually, if its acting as a qualifier for an adjective (like goed), it goes first, just like the english "not good", but when it refers to an action not being done it goes at the end
If an adjective comes before a noun with a definite article ("de" or "het"), it usually gets the ending -e.
- de goede vraag (the good question)
"vraag" is singular and a de-word with a definite article, so "goed" gets the ending.
- de goede** vragen (the good questions)
"vragen" is plural so it gets the ending
- het goede idee (the good idea)
"idee" is a het-word with a definite article, so "goed" gets the ending.
If the indefinite article "een" comes before a het-word in the singular, then the adjective (goed) does not get the -e ending:
- een goed idee (a good idea)
If it comes before a de-word, it does get the ending.
- een goede vraag (a good question)
If no article at all comes before a het-word, then the adjective does not get the -e ending either.
- goed idee (good idea)
If no article comes before a de-word, it does get the ending:
- goede vraag (good question)
Also, if the adjective does not come before any noun (like here for instance, or "De jurk is blauw."), then it does not get any ending.
I translated this as ''Geen goed". What is the difference in usage of ''geen'' and ''niet'' for ''not''?
Geen is used before a noun.
For example 'Ik heb geen geld', which means 'I have no money' or 'I don't have any money'.
Niet is used before a verb.
For example 'Ik wil hem niet zien', which means 'I don't want to see him.'
I used "Nee", which was counted incorrect, what is the difference between "niet" and "nee"
This might help: https://www.duolingo.com/comment/3734833/Grammar-niet-and-geen