Some very old films age better than others. I'm afraid this is one that hasn't aged too well. Possibly because the screenplay was written by Thea von Harbou (Mrs. Fritz Lang), who was never all that bothered about narrative logic, it doesn't make much sense. The hero's financial woes appear to be conveniently sorted when, early in the film, a beautiful and incredibly rich Russian princess he's never even met suddenly informs him that, for vague reasons involving events we don't see, she wants to marry him, which really ought to be the deus ex machina in the last reel, but instead drives the entire very confusing plot, in which by a series of amazing coincidences the main characters all run into each other while wandering around Europe, but mostly don't know it because they're pretending to be other people, and some of them go to a lot of trouble to do things which will be important later, although they don't know that yet so have no reason to do them.
Even more of a problem is the humor. There's very little in this comedy that's actually funny, and what there is tends to be bizarrely random, as if the production team weren't quite sure what a joke was. For instance, one character, for no discernible reason, has a large pack of dogs which he's trained to run races through his house. And the most memorably weird scene involves one of the baddies encountering two strange men who somehow make a living by pretending to be zoo animals, which they apparently do all the time, even when there's nobody watching. None of this has the slightest relevance to the plot. Our heroes don't ultimately save the day by using trained dogs and men disguised as ferocious African wildlife. These oddities simply pop up for no reason at all whenever there hasn't been anything to laugh at for a while.
Alfred Abel, usually typecast as a doomed neurotic, is obviously having a lot of fun playing a gleefully amoral but ultimately good-hearted gentleman rogue, and he does at least know he's in a comedy. He even tells a joke or two. But some of the other casting is peculiar to say the least. Watch out for Max Schreck of "Nosferatu" fame as one of the quartet of ragged idiots who make up the entire revolutionary guerrilla army of the Grand Duke's wicked rival. This fearsome foursome look so weird that they're more like trolls than human beings, and one of them has a hunchback and capers about in a desperate attempt to be funny, so I think we're supposed to find them comical. But in fact they're genuinely menacing, and the things they're given to do, such as attempting to hang someone, don't include any actual humor. Nine years later, the Marx Brothers made "Duck Soup", some themes of which are so similar that I think this movie may have been an influence on it. Only the Marx Brothers remembered that comedies ought to have jokes.