Translation:Do you have this dress in size forty?
When you're in a shop and you want to ask if they sell/have something, is it most correct to use the plural you (dere)? Thx.
Unless it's a shop entirely run by a single person, "dere" feels more natural to me. However, there's nothing wrong with using "du" either.
If I were to wager a guess, I'd say it's because it just sounds pretty old-fashioned =S Or possibly regional? I can't speak for the entire Anglophone though. "Do you have..." just sounds much more natural ^^
For listening exercises, we're unfortunately only able to accept exactly what was written in the source sentence. Using the numeral isn't wrong, it's just a technical limitation.
Please someone explain "Denne" and "Dette". I swear I've done other exercises where "Dette"="This" and "Denne" means "That"
It's a European womenswear sizing thing - size 40 = US size 8 = UK size 12. Here's a more detailed chart (I picked Asos at random, but if the link doesn't work, any womenswear retailer who sells international brands will have a conversion chart: https://www.asos.com/infopages/SizeGuide/pgesizechart.aspx )