This is not specific to this exercise, but how common is sarcasm or irony in everyday Swedish? I bring it up here because if I said or heard the phrase 'what a joy' in English, it would be as a sarcastic remark to something mundane or irritating.
Irony is very common in everyday Swedish, and "vilken lycka" could definitely be used sarcastically. It depends on the context.
I had heard that "lycka till" was "good luck" is this not correct or is that that it doesn't mean that, but it's used in the same context for English?
I have come across several examples of lycka that Folkets lexikon provides to the meaning of "luck". Lycko|sam, fiskelycka, jag hoppas att du lyckas, and of course "lycka till!" Are they all obsolete and not usable in the contemporary language (with the exception of the last one )?
Sure, I was referring to "lycka" as a separate word, which nowadays seldom means "luck". There are a few remaining constructions that have the connotation "luck" and that are still used, such as "lycka till".
I think the confusion stems from the fact that "lycka", when not meaning "joy", has come to increasingly blend with the meaning of "lyckas", "to succeed". It's a very fine line, but that's why "jag hoppas att du lyckas" actually means "I hope you succeed", rather than "I wish you luck", which would be "lycka till" or literally "jag önskar dig tur".
Your other examples, "fiskelycka" and "lyckosam", while retaining some of the connotation of "luck", could be interpreted in the sense of "fishing success" and "successful", and in the case of "lyckosam", I would say that this is actually more common. It's a beautiful word and I encourage you to use it. But if you want to make sure the reader reads it as "lucky", "tursam" would probably be a safer option. It depends on context. For some usages, check out http://www.synonymer.se/?query=lyckosam .
You can phrase this as "What happiness?" and you will get marked correct. A lot darker than what Duo wanted me to type.