Learning vs. translating
I just started, and I'm being prompted to translate very difficult long, involved sentences. You'd think that wouldn't be the case considering that I'm learning things like "i am a boy". Why is this happening?
Well, I don't really know much about duolingo's process of education, but it seems like that isn't helping anyone learn anything. Did you know that you can "peek" at a word to look at it's meaning? Maybe the idea behind the translation is not to know what the words mean, but to be able to express them in another language using correct syntax and grammar.
You're being asked to correct other people's translations (presumably people who are learning your native language). I think duolingo just hasn't implemented a filter to match the sentences you're asked to translate to your actual skill level.
Translating is about more than writing down the literal meaning of a word. Sometimes the translation suggested by Duoling for an individual word is not the best one, so you as translator have to know whether that particular translation works in the context of the rest of the document, or even in that sentence. If it doesn't and you don't know that from your own vocabulary store, go and look it up in a dictionary to find other ways to translate it. This is incredibly hard when you're just starting to learn a language, but the more you're exposed to your target language the easier it will become.
You don't have to do this immediately...it is the final step in the process, I think you should come back to the translation parts when you feel comfortable enough, I don't see a problem with it since its not required to "move-on"