what are the funniest cases of false friends in German and English?
Oldtimer is a classic. In the US and elsewhere, people think of an older gentleman. If a German is talking about an oldtimer, we mean a car older than 30 (?) years. The term is mostly used for classic old cars from the 1960s or before. We have entire Oldtimer clubs, which is a bunch of people who own and drive old cars for fun.
There are a number of German words that were invented in recent years and decades that sound like English, but aren't. Classic is the very common word
Handy. That means cell/mobile or smart phone. A lot of people think it's an English or American word, but obviously neither Americans nor Brits are familiar with that word.
Beamer is another one. Americans and Brits used to call it projector.
What I find interesting in politics is only some titles have a German word for the tenure. Presidency obviously means
Präsidentschaft (President/Präsident is very similar), Chancellorship means Kanzlerschaft (chancellor/Kanzler), but there is no word for governorship. Governor means
Gouverneur in German, but nobody would ever say "Gouverneurschaft". Neither does a word for speakership exist in German. Ambassadorship is another case: Ambassador means
Botschafter, and "Botschafterschaft" doesn't exist of course.
Botschaft exists, but that means Embassy.
When it comes U.S. states, only California has a Germanized name
(Kalifornien). All other US states are called the same. And California and Texas are the only one with an adjective for Californian or Texan
(kalifornisch/texanisch). Nobody would call something from Ohio "ohioisch" or from Oregon "oregonisch". I've rarely read
pennsylanivisch for Pennsylvanian, but that is rarely used (I assume a holdover from German immigrants or so).