I only found this on scenery-chewing:
"Dear Word Detective: "Chewing the Scenery" -- I've seen this phrase used periodically over the years but it seems to be extremely popular recently when describing someone's acting (or should I say "over-acting") in a movie. Where did this phrase come from? -- Sean Ford, via the internet.
Good question. Of course, "scenery-chewing" is no longer just found in movies. Now that showbiz has gobbled up TV news, viewers must endure the sight of newscasters and correspondents carrying on as if they were auditioning for a grade-school production of Hamlet. And it seems to be spreading. While hyperventilating "you're-not-gonna-believe-this" histrionics have become standard in the American media (take Geraldo Rivera, please), I was shocked to see a reporter on the normally staid BBC last week waving his hands and wiggling his eyebrows as if he were trying to levitate. I believe he was talking about sales tax.
To "chew the scenery" means, as you say, to overact or perform in an extremely melodramatic fashion. "Chewing the scenery" is generally regarded as the hallmark of an inexperienced or untalented performer, but many fine actors have gone a bit over the top on occasion, and in the right context, especially in an otherwise boring production, a little chewing can be fun. Johnny Depp's flamingly weird performance in the recent "Pirates of the Caribbean," for instance, rescued what, in my opinion, was a depressingly pedestrian and predictable movie.
"Scenery chewing" is, as you might suspect, hardly a new phenomenon, and chances are that quite a few of the plays presented in Ancient Greece were marred by over-enthusiastic performances. But the phrase "chew the scenery" itself is an American invention and apparently dates back only to the late 19th century, the first print citation found so far being from 1895. The idiom almost certainly originated on the theatrical stage, where an overly-dramatic actor's fervid antics might well have been metaphorically likened to seizing and biting pieces of the painted scenic backdrop."
I'd say, it describes what I'd call "übertriebenes / überdrehtes Verhalten" in German.