The query "Penis … rosa: stuk onbenul (4) letters" appears to be a riddle or puzzle in Dutch, asking for a four-letter word that fits the clues provided.
The answer to this riddle is "ROOS," which translates to "rose" in English. This fits the context of "penis" and "rosa," as "rosa" is the Latin word for rose, and "roos" is the Dutch equivalent.
Thus, the solution to the puzzle is:
* Answer: ROOS