The prepositions translates differently in different contexts. It is one of the really difficult things to get correct for non native speakers. You just have to remember which goes where.
You can say drikker kaffe i en kafé for this one, and be correct. But the set phrase for going out with friends to a café and drinking coffee (and maybe something to eat) is gå på kafé hence drikker kaffe på en kafé as the preferred translation.
Takk for svaret! I actually did a bit of sleuthing myself after posting this, as I was thinking perhaps it was some remnant of Indo-European that had magically been lost in most other languages. A nice fantasy. :-) As you say, på comes from Norse (Old Norse?) opp på 'up on'. Meanwhile, it seems that Russian по comes from an earlier Indo-European root meaning something like "from" or "after", depending upon where you look, but clearly the two of them are not directly related. So it is, as you say, a coincidence, though it is somewhat eerie how similarly they are used.
Thanks again for replying! I do always enjoy your posts!
"På" translates to "on", but it's usage is different from English. Thus it is used in several specific circumstances where it translates as "in". However these are not all the English uses of "in", and there are many circumstances in which it's wrong to use "på" to say "in".
Typically "på" translates to "in" when combined with specific place names:
Normally you live "på landet"/in the countryside, "i byen"/in the city, "i" a street address, "på" (but sometimes "i") a city borough, "i" et fylke /in a county, "på" ei øy/on an island, and then there are certain parts of the country & municipalities & towns that require "på" instead of "i".
Then there are places, activities & institutions: på skole, på kafé, på sykehus, på ferie...
This is one of those memorization things, isn't it? I'm thinking that with enough repetition my brain will remember it whether I mean to or not. Things like this remind me why it is best to learn languages in phrases, not just vocabulary (Individual words). Thanks for your thoughtful answer.