I favour tough, a good translation which didn't occur to me until Duo suggested it.
Heavy (to mean difficult) was widely used colloquially in 1970's UK by students and hippies. E.g.:
- I study medicine. – Heavy!
- I'm learning Polish. – Heavy, man!
- My bird wants me to meet her Mum, can't get my head round it.
– Really heavy, man!
[5 Feb 2019]
Yes. 'Swaar' can mean both physically heavy as well as figuratively 'having a hard time' in Afrikaans.
Although in translating this specific sentence, one would say 'hierdie onderwerp/tema is moeilik', never 'hierdie onderwerp/tema is swaar'.
'Hulle kry swaar' (literally: 'they are getting heavy') translates semantically to 'they're having a hard time' (referring to financial or other difficulties).
As for Dutch, I haven't encountered an instance of this sentence directly, but I would presume it would be more or less the same situation.
Incidentally, I don't know if it's a coincidence, but the word "Ciężki" seems to be used as a family name:
"Mr. Heavy"/"Mr. Tough"?
Hmmm... I guess you're right, I may have been too quick to dismiss that answer.
Especially that I checked now and actually "difficult" was accepted already...
Well, "trudny" can just mean complicated, difficult to learn, but you're right, also something that is not easy to talk about, because it's very sad, serious, etc.