German, French, Ancient Greek/Latin (of the two I would choose Greek), maybe Mandarin or Arabic. If I had to pick two: German and Ancient Greek (assuming you don’t mind studying a dead language)
Yes, specially when it comes to slangs and other day by daystuff. Also the accent, european portuguese has very strong consonants and very short vowels in general, here in Brazil our vowels are more distinctive. Also the portuguese are more formal about the 2nd person, here 2nd and 3rd person are often mixed (but not confused). Also we brazilians are more open to foreign words, while in Portugal they like to translate almost everything, even if it sounds awkward.