Translation:I step into the room behind the beautiful young kindergarten teacher.
In the US, "kindergarten" is different from "nursery school," which is more commonly called "preschool". Specifically, preschool (and/or nursery school) is an optional program for very young children (e.g. 3-5 year olds) which occurs prior to the start of official schooling. On the other hand, kindergarten is typically the first year of official schooling. (After kindergarten, grades are numbered: 1st, 2nd, 3rd, ... 12th.)
I have a suspicion that the Hungarian "óvónő" (whom we have learned so much about) is more analogous to what Americans would call a "preschool" or "nursery school" teacher rather than a "kindergarten" teacher, but I would love to learn more about this from some native Hungarians.
(Though, it might also be nice to see a few more practical sentences and a bit less of the miraculous flying óvónők in this course.)
An óvoda (or a Kindergarten in Germany) is the place you stick your children in over the day while you're at work and the children are too young for school (so usually about ages 3-6). Kind of a daycare, but with practical and social skill teaching elements. I think it's closer to the American "nursery" here.
I, too, am curious about the recurring (and apparently deeply memorable) kindergarten teacher. I would like to chime in in favor of middle school teachers, whom I found to be powerful and occasionally enchanting role models as a youth. At least the course designers have a sense of humor.
This is the most stupid, frustrating course ever. It insists on its own mistakes over and over. So far, it is the only thing capable of making me dislike the language, something I thought impossible. It is a shame, especially because other Duolingo courses for languages harder than Hungarian are encouraging and reasonable.
"Nice" has different connotations, depending on whether you're talking about a person (or an animal) or a non-living object. In regards to animate objects, "nice" means they behave in a kind way. Friendly, generous, altruistic, the like. You'd express that with kedves in Hungarian.
For inanimate things, "nice" is not about the behaviour (because inanimate things most often don't have one), but about physical aspects - they just look good. That's why szép can be translated as "nice" when talking about non-living things, and only "pretty" or "beautiful" when speaking about humans.