Native/fluent speakers of languages other than English: please send me an idiomatic translation of the following phrase, and a list of words (excluding stopwords) that you would expect a correct stemming process to result in:

"Can you believe that? Unbelievable!"

(I'm integrating various stemming libraries into an anti-capitalist search engine project and would like to verify that it works correctly for as many languages as possible, at least on a basic level!)