No -- hin and her act differently in this respect.

This is one situation where the German sentence is actually simpler than the English.

Ok, so we want to "pay for something". Like, you've ordered food in a restaurant and now you need to give money for it. The verb for this is German is bezahlen. In English you usually need a preposition as well: the word "for", as in "We pay for the food". German does not need a preposition: It's simply Wir bezahlen das Essen. The direct object of bezahlen is the thing being paid for.

There are many other ways of adding more information to this simple sentence. You could ask "How do we pay for the food?" or "Who pays for the food?" or "Where do I pay for the food?". The question here is "With what do I pay for the food?" (i.e. "cash" or "credit card" or "Euros"). In English you've got the flexibility of splitting the "with what", giving the phrasing in Duolingo's example. In German, that's not possible here - because "with what" is actually one word in German: womit.

You might thing that it should be mit was but that's not so. There's a general category of German 'question-words' that are made up of wo- and a preposition. You can think of it as a compulsory contraction, if you want. You've got womit, wovon, wonach, wofür... and sometimes you need to add in an extra letter to make it sound good: woraus, worüber, worauf.... You can find more information about these words here.

When asking a question in German with a question-word, it goes first. Then you've got the verb in second position as usual. The subject then has to come next, because it's been bumped out of first spot. Duolingo explains questions more on the lesson tips page.

Lebensmittel is almost always used in the plural: die Lebensmittel.

In the singular, I suppose it might be something like "the foodstuff". Or perhaps "the victual", to give an idea of how rarely the singular is used.

Also, it's important to remember that Lebensmittel are basically raw materials. They're the things you buy in a shop.

Once you've prepared them, cooked them, especially if you've combined several raw materials together (e.g. potatoes + leeks + water into a soup), you have Essen rather than Lebensmittel, though in English you can call both of them "food".

wem is the dative of wer, so mit wem means "with whom".

"with what" is womit or, sometimes, mit was.

was doesn't really have a dative case; with prepositions, it usually appears was wo(r)-, and inanimate things don't usually act as indirect objects.

You are correct, "What do we pay for the food with?" is a bit unusual for an English speaker to actually say. It's not quite how people would talk. If I were in such a situation to say such a comment I'd probably say something like:

"How are we paying [for this food]?" (meaning, with what and by whom),

or "What are we paying with?" (assuming we just now discovered we have no money)

There are many ways to say the same things. But, with Duolingo, they seem to toss us the most unused, unusual, and unnatural word phrases I've ever heard. It would be nice if the phrases they gave us were things we could actually use: "I don't see my bike.", "How much is the pizza?", "Where is the train station?", "Is the restaurant open?", "More beer, please!"

But, "The bear drinks my beer", "The humans are reading a newspaper", and "My cat wears trousers" are all phrases never spoken by mankind for any reason what-so-ever. Maybe a bit cute and funny at first, but come the 50th it's just annoying.

"With what do we pay for the food?" could work, and it does avoid ending the sentence with a preposition. But Duolingo's sentence sounds much more natural.

• für is misspelled
• Essen is miscapitalised
• was ... mit cannot be split up like that; it has to be womit

'with what'

Eh? What kind of "natives"?

Also, womit is a German word and vomit is an English word (and it doesn't mean "belch", at least not to my knowledge). They're not (usually) stressed on the same syllable, either.

I don't think that pair would cause a lot of problems.

I think learners tend to have more difficulties with wo = where and wer = who, or with the fact that sie (in German) and you (in English) seem to have so many meanings.

I hope they will ask to answer at some point

Essen, not eßen.