Learn German: Vielen Dank, ich möchte kein Geld. - Many thanks, I do not want any money.

It comes from an older, longer phrase meaning 'I give you many thanks'. Because der Dank is a masculine noun and acts as the direct object in that hidden sentence, the adjective takes the -en ending. At this level, it is best to just memorize Vielen Dank as a fixed phrase.

Why does the German use möchte (would like) if the English translation is 'do not want'?

In German, ich möchte (I would like) is the polite and common way to express what you want, even when saying no to something. Using the literal translation ich will (I want) can sound very blunt, childish, or demanding to native speakers.

Why do we use kein here instead of nicht for 'not'?

In German, when you want to negate a noun that doesn't have a specific article like 'the' or 'a' in front of it (in this case, just 'money'), you must use a form of kein. You are literally saying 'I would like no money' rather than 'I do not want money'.

Why is the word exactly kein here, rather than keine or keinen?