"I made a suit at the department store"
デパートで せびろを つくりました。
What does that even mean? They have a secret sweatshop in the basement where people make suits? Or: you found a jacket and pants that go together (but then it wouldn't be a "suit", more like an outfit)?
What do you think?
I think it's another one of those sentences that don't completely make sense, like the: "My dog sells hats", "I party 24 hours" or "I take off my clothes in winter". ;) They're just for demonstrating the use of new words, while not being logical. Maybe they wanted it to say "I had a suit made [for me] at the store".
I imagine English must be just as confusing for the Japanese as Japanese is for English speakers. Idioms, nonliteral translations, words that change meaning depending on context...
I think the sentence means (I had a suit made at the department store). Another way of saying it (which would've probably been less confusing to the learner) is デパートで せびろを つくってもらいました, which is slightly different from the sentence you gave in that it refers to the speaker as the "recipient" of the service of making the suit through the verb もらいました. But your sentence is used too and does convey the intended meaning.
One more thing: within my exposure (so take with grain of salt here), I have not heard anyone use the word せべろ. People always used スーツ for Suit (It seems to be an increasing trend in Japan to choose loanwords over their Japanese equivalents).
I wouldn't be able to resist either xD The Japanese course creators surely have to be fluent in English, but this "hat-selling dog" really is the inside joke of the course. And it gets even better if someone reads the sentences' comments section, too. Well, nobody can say now that learning languages isn't fun ^.^
I'm halfway through the Esperanto tree, now that's a place full of wicked sentences, a real treasure trove...
For example: The ugly baby dances fast and the comments there are priceless ;D
And right now I ran into: The cat punished the kitten because it kissed a mouse.
I've got the impression that the Esperanto creators are a bunch of really funny people ^.-