If you have previous experience with a language and feel that lessons are too easy, there are several ways to advance more quickly, skipping ahead by unlocking grayed out skills and lessons.
1. Take a placement test. This option is available the first time you start a new language tree to make sure you are placed in a spot that isn't too easy for you.
2. If you would rather unlock/test out of many skills at once, you can click on the checkpoints (Castle icons) found throughout your skill tree on the home page. Passing this Checkpoint will unlock all skills in the tree up to that point to level 1. Once a Checkpoint quiz is completed, it cannot be undone.
3. Test out of skill levels individually: You can complete a skill test to jump to the next level of any skill*. Simply tap the skill, and then tap the Key icon. If you get more than 3 questions incorrect, the skill test will end.
All in-app users can complete a skill test from level 0 to level 1 for free. After level 1, you will need to use gems to complete a skill test. Duolingo Plus subscribers have the perk of unlimited skill test-outs.
*Grammar skills will not have this skill test-out feature as they usually encompass 1 or 2 levels.