Hi @ all... I'm German, but live in the UK for several years...
Please don't forget that kids/young adults today don't learn languages just for fun - they do it for life & work, especially where lots of borders within European countries are gone and you can travel and work wherever you want...
It's a huge advantage to study German, because it's spoken by almost 150 Million people worldwide (I bet you didn't know that *lol* - shocked ??). here some countries where German is spoken: Germany (of course *lol*), Austria, Switzerland, Liechtenstein, Luxembourg, Netherlands, Denmark, Eastern Belgium, Eastern France, North Italy - then in parts of Poland, Czech Republic, Slovakia, Romania, Hungary, Kazakhstan and Russia... also in Namibia (a former German colony), Brazil has ~5 Million German speakers, Argentina and Mexico together around 1 Million and don't forget that 15% of the American population have German ancestors and (unbelievably) for over 7 Million people in the USA German is the first language !
Yes, I'd say that learning German isn't a bad idea...
French comes right after German with around 130 Million - I don't like French, so I won't list all the countries where it's spoken *lol* ... ok, ok... in France (obviously), parts of Canada, Cameroon, Haiti, Rwanda, Belgium, and in a couple more countries...
Spanish with over 390 Million native speakers comes after English (~ 510 Million)... for that reason I recommend to learn Spanish too, but I won't write down the endless list of countries...
Or learn Mandarin, which is spoken by more than 1 Billion (1,000,000,000 !!) people in this world ;-)