It should be "I broke fast", not "I breakfasted", there's already a verb in there but people have forgotten, TBH "To have break fast" is quite questionable grammar. It's different in German, "Frühstück" means "early piece", an adjective-noun compound which then can be fed through the usual verbification rules.

From what I have gathered. In German you can just make up words, it it makes sense everyone will just go along with it.

There are a lot of words in English that could exist but if you made them someone would look at like you are stupid for thinking something that isn't a word is a word. You can't just make words.