Questions & Answers about Если у нас останется ещё одно киви, завтра я добавлю его в смузи.
Russian usually expresses possession with у + genitive rather than with a verb like English have.
So у нас останется literally means something like there will remain by us or more naturally we will have left.
A useful way to see the structure is:
- у нас = with us / by us
- останется ещё одно киви = one more kiwi will remain
This possession pattern is extremely common in Russian:
- У меня есть книга = I have a book
- У нас осталось два яблока = We have two apples left
In your sentence, the thing that remains is одно киви, so the verb agrees with that.