Responses
It does state that he's merely "helping out" at the ramen shop since it's run by his uncle but it was mentioned (forgot which chapter) that he also has a full-time job. One which requires him to be in tip-top shape.
Edit: please ignore the last sentence. His work and age remains undisclosed as the mangaka layered over his words when he was asked with regards to the them.
We do know he's no more than 25 y/o from some clues. He has a main job, part times at the ramen shop and does some volunteering on the side. (see chapter 58)
Was the Ramen shop his actual job and what’s his age and why does he know so many facts since they always crossed that out for the joke