How can I skip a category/lesson (like animals)? oolala
When you go to a new category, all the lessons will be listed and to the right is a big icon that says "0/7 Lessons completed" (depending, of course, on how many lessons are in that skill set). Just beneath that there is a yellow oval with a lock and the words "Test out". Click that. Take the test. Pass it. Ta-daaaah!!
I don't think you get any XP for testing out, but you do get to progress down your tree more quickly and skip topics that you know inside and out.
You can't do that. In addition to introducing zoo animals, Duo will be slipping in other new information that you will need to progress through the other levels. So even though you are learning "animals" you will learn things like "The elephant drinks milk" and later on when a new verb tense is introduced, you will be expected to also know "milk" and the verb "to drink" so that "I drank milk yesterday" and "When I was a child I used to drink milk" allow you to focus on the verb conjugation rather than the vocabulary.