how can I open the lesson 2 box?
To open/unlock the lesson 2 box you have to do all the units of lesson 1, meaning you have to learn lesson 1 first. Welcome to Duolingo by the way.
Or you need to do sufficient translations that contribute to lesson 1. Or you can do the Mastery test in the top right corner. Be aware you only get 3 goes to pass this (but you can abort the test). Also, if you mouse over the progress bar, it tells you how many points you need to "learn" and how many points you need to "master" the lesson. You only need to "learn" a lesson to open the next lesson in the skill tree.