"Flott" can also mean 'cute' or similar words, but it's not appropriate in this context.
Several Norwegian nouns end in -er in the singular indefinite form, and they just get an -e in plural. Too many "erer" or "enene" just becomes confusing, I guess.
He's = he has, but only when "has" is an auxiliary verb and not when it's a main verb. (apart from in dialects like in Irish English). Duo can't tell these two contexts apart - it happens in the other language courses as well when Duo generates "correct" or "alternative" answers.
"He's great teachers"? Because that's how it corrected me and I don't see any sense in it.
You can write "he has" as he's. As well as "he is" = he's. He's great at teaching. He's got a great teacher.
Contractions aside, "he's great teachers." Still doesn't make grammatical sense. Perhaps is meat to say "he has great teachers"?
"He has great teachers" is the preferred answer. It is allowed within English grammar to contract "he has" to "he's" as far as I know, that's why it is added as an alternative.
I believe that in most parts of the English-speaking world "He has a great teacher" would not be shortened to "He's a great teacher" partly because most people would understand the latter as "He is a great teacher". But I suppose there are areas in the world (UK?) where this is OK. Otherwise shortening "he has" to "he's" when followed by a past participle as in "he's been a great teacher" is normal. Feel free to correct me if I'm wrong :)
No, we can't shorten "he has" to "he's" in the UK, or anywhere that I know of (unless we say "he's got"). I believe the accepted contractions are automatically generated and this is a glitch in how it works. Certainly that's the case in the Russian course.
I think it is more acceptable is certain situations like "He's eaten" which would be understood as "he has eaten". I don't think that "he's" is appropriate in "He's great teachers", that would universally be understood where I live as "He is".
"He's great teachers" is not one of our manually entered alternatives. So if this still shows up it is because it is a part of the language base. Something I think we can't alter...
Would the definitive plural of teachers be lærerere? How would you pronounce that?
Why does this sound like it is saying "lar-de-da"? Where are the D sounds coming from?
A "tapped r" is made by touching the tongue at the same point that is used for "d" - the contact is just less firm. The two sounds are very similar. If context leads you to expect a "tapped r", you'll hear "r", but without context or without previously knowing the word, it's totally reasonable to interpret the sound as a "d".