What is the difference between using у and в here?
basically whether it sounds nice. We tend to put U at the beginning of the sentence and between consonants: U richzi (in the river).
Yes, it was in Occupations lesson:
у - after consonats and at the beginning of a sentence
в - after vowels
But does not "у" also mean "at" in the sense of visiting? For example when saying "going to the doctor" or "I am at the doctor":
" Я у лікаря".
Or am I wrong? Really confused now
Yes, у/в can also mean at, but they are interchangeable. Я в лікаря is also fine.
"Я не маю кави." is also another correct way of saying "I do not have coffee."
Yes, it's accepted. To me it shows, since two years ago. So maybe it was added after your comment :D Then, thanks! Or maybe you had some typo, stuff happens.
Duolingo wants all words to be fancy so that's why I got it wrong 6 times in a row
Could you specify what your issue was? What was your input? What was the error message, why wasn't it accepted?