have some fun with words! - umfahren
is a funny thing about the German word "umfahren".
It is just a joke, pls do not be encouraged. You do not spell them the same way: The thing, which knocks you down, is spelled as UMfahren, the thing, which goes around is pronounced umFAHREN. And it is an abbreviation (oh yes, the bad news, a valid one): The thing, which goes around is for HERUM-fahren. 'herum' is something like circle around. Shortened to "um", and then yes, if you read it, then in very, very rare cases, you do not know if it is - or the opposite.
You know what? Say "niederstoßen" instead. It is more common.
I would prefer "niederstoßen" before "umfahren" in doubt. The differences are more felt, than grammer. I rather would prefer niederstoßen for a person and umfahren for a thing. E.g. "Mister Minit wurde gestern früh von einem PKW niedergestoßen." or "Der alte Mann hat das Verkehrsschild einfach umgefahren!" but you can say as well (although I would not prefer): Mister Minit wurde von einem PKW umgefahren. and Der alte Mann hat ein Schild niedergefahren (hier vielleicht 'überfahren') It is a question of feeling and personal style.
And yes, "herumfahren" means to drive around aimlessly. But as well, it means 'um etwas herumfahren'.
E.g.: Der alte Mann ist um das Verkehrschild herum gefahren. Diesen Verkehrsstau wollen wir umfahren!
herumfahren means a lot of things: https://www.duden.de/rechtschreibung/herumfahren
No, this is not because German is hard. English words mean a lot of things as well. It took me decades of learning both languages (today I cannot speak neither of them any more, forgot my German and did not make it in English) to find out, that something like a matching translation of vocabulaies does not exist.
Gutes Gelingen! Cherrie
I'm always puzzled about all the things we never think about when it comes to our own language. Thanks a lot for the input.
If I may add some aspects/corrections:
The spelling is exactly the same, just the accentuation is different.
Also I wouldn't agree, that umFAHren is an abbreviation. You say "etwas umFAHren" or "um etwas heRUMfahren".
Last but not least: niederstoßen is slightly different than UMfahren. The latter one involves "fahren" so you need to drive a car or ride a bike.
about: "niederstoßen" formal / common: I agree with formal, but not with uncommon. I expect it to read it in newspapers, accident reports or legal textes. I never wish anybody to be involved in an accident with persons insured in a German speaking country. But if he is, he shall understand the police protocol.