Probably he becomes a reasonably skilled architectural draftsman, working for an architectural / engineering firm, or perhaps a mechanical designer/draftsman working for a major railroad. I'd assume he'd grow up in a city with a sizable German-speaking population, which would suggest Baltimore, Buffalo, Chicago, St. Paul, Milwaukee, or Cincinnati. I'll go with Baltimore since that's the one I know best, and besides, at the beginning of the 20th century, approximately one-fourth of the population of that town spoke German.
So...he becomes a designer/draftsman in the engineering department of the Baltimore and Ohio Railroad, working his way up slowly, until he's the head of the drafting room by the early 1930s. He takes night school courses at Hopkins during the same period, earning his degree in mechanical engineering. By the mid 1930s, he's promoted to second in command of the engineering department, and becomes the honcho in the early 1940s. He retires at the mandatory age of 65 in 1954.
Outside the office...hard to be sure, but chances are he leads a relatively ascetic life, is a regular at Mass at Baltimore's cathedral or perhaps a neighborhood church in Highlandtown (a part of Baltimore that used to have a sizable German and Polish contingent; today, it's mostly Greek). He partakes of a beer now and then at one of the Highlandtown beer gardens, has a meal once in a while at Haussner's Restaurant on Eastern Avenue, and spends much of his spare time sketching and painting landscapes and the like in Druid Hill or Patterson Park. He's not a big follower of sports, but once in a while goes with a few friends to a minor league Orioles game at the park on Greenmount Avenue. It's likely he never marries.
His obituary warranted perhaps a sixteenth of a page in the Baltimore Sun upon his death at age 74 in 1963, covering his career and night school education for the most part.