"Will you cosplay with me?"
Duolingo could have included things like Hanami under "Culture". They could have discussed the Hina Matsuri and koinobori. Why Japanese folks get special photos of their kids at ages 3 and 5 or 7, that would be interesting. What about Bonenkai? Tanabata? Even more recent things like the Japanese take on Christmas would be good introductions to the culture.
Instead, we get a "Subculture" section with "Will you cosplay with me?" Ugh.
Well, the three "bonus skills" are meant to be: "Olympics", "Subculture", and "National Holidays". I think most of the things you mentioned would instead be found in that National Holidays skill if it existed/exists. ^^
* Scroll down to the part titled "Bonus Skills" on the Japanese course incubator page:
ませんか is how you issue an invitation in Japanese. Functionally, it means the same thing as "Would you like to do ....?" This is covered in Chapter 3 of the Genki I textbook.
When issuing an invitation in English, you might say "Won't you have dinner with me?" However, "Would you like to have dinner with me?" or "Will you have dinner with me?" are far more common.
If I read "won't you cosplay with me?" without context then I would assume that someone thought that they were going to cosplay together and he/she asks this in a bit of a surprised way after finding out that they're not going the other person didn't intend to cosplay with them.
And if I read 私と一緒にコスプレをしませんか I would read it as an invitation to cosplay together.
While "won't you cosplay with me" could be correct, I think it only really works when spoken. In text it would be more likely to write "will you" or something similar.
I'm not a native English speaker though, so I could be wrong. But I do believe that there is at least a decent amount of truth behind my statement ^^
'わたしといっしょに' absolutely is this order.
’いっしょに’ means just 'together' or 'with'. 'わたしといっしょに' is 'together me' or 'with me'. Therefore they are used together well. I think they are especialy not a set phrase.
Please add sugar with salt.
(I hope that somebody repair to about my English sentence.)
So there's an exercise in this same lesson which has "コスプレをします". But if I use を after コスプレ for this answer it's considered wrong! I refuse to believe it makes a difference whether it's a question or not... Also it's interesting that the Windows IME doesn't automatically generate コスプレ.
私と一緒にコスプレしませんか. Marked as wrong. わたしと一緒にコスプレしませんか also marked wrong. It's not going to let me use any kanji here, which is inconvenient because my computer wants to automatically convert kanji. It's an extra step for me to go back and undo it so it does't use the kanji... hmm...