Help me with this sentence from duoling.

Daniel, I do think that you were technically correct in the way that you translated DuoLingo's sentence.   I think the problem is that DuoLingo had difficulty figuring out how to write something in Spanish that would make users translate it as "went _____ing."  The tricky thing is that there doesn't seem to be an exact Spanish equivalent for how we say some English verbs as "go ____ing" or "went _____ing" (go fishing, went dancing).    It is not a common grammar structure in English; there are a small number of verbs that can be written "go _____ing."  (Most of those verbs are for fun leisure activities such as go swimming, go bowling, go camping.  Since some people think that shopping is fun, "go shopping" is commonly said).

So, if DuoLingo had asked you to translate, "Esquié," users would probably write, "I skied" (which is correct).   But when DuoLingo asks users to translate, "Fui a esquiar", some users will (correctly) translate that as "I went to ski" instead of the "I went skiiing" that DuoLingo is hoping to have users practice saying.  To help users be successful in translating the verbs the way DuoLingo wants in that exercise, DuoLingo should probably give a hint such as, "Write your answer in the format "go _____ing" or "went _____ing.""

Here is a website that has more examples of verbs that can be written as "go ____ing" https://englishwithkim.com/go-ing-gerund-fun-activities/

If I went somewhere to ski and I did ski...then the way I would say it is, "I went skiing last winter." 

If I went somewhere to ski, but I couldn't or didn't ski...then I would say something like, "I went to ski, but there wasn't enough snow and the ski resort was closed." 

Perhaps "I went to ski" is best used to generally talk about having had an intention or plan to ski?   I don't think it makes it clear that you DID actually go skiing (maybe you did, maybe you didn't...the listener will have to wait for you to say more).

I think this is true for some other verbs when they follow "went".   For example: 

We went swimming last weekend. //  We went to swim, but the water looked really dirty; we decided to take a hike around the lake instead.

We went hiking in Yosemite National Park.  //  We went to hike, but my friend twisted her ankle.  So we spent the day riding the bus to see all the great views.

Here's a link to a forum where some other people discusses whether to say "went skiing" or "went to ski":

https://forum.wordreference.com/threads/to-ski-vs-skiing.342131/