where are the lessons?
Where are the lessons? grammatical instructions for example? there are only exercises here, but any lesson!
For some skills there are grammatical explanations on the skill pages. For the other there are none, but there is plenty of information in the internet that you can use. There is also quite a lot of useful information in discussions. Read the most popular discussions in every skill, look into discussions of every sentence you learn and many questions will be solved right away. The team is working on better grammar introductions and grammar tips in the lessons, but Rome was not built in a day. I can say the grammar explanations are now much better than they were before.
Don't hesitate to make a search if you don't understand something. Here is a great guide with examples for beginners: http://duolingo.com/#/comment/370405
Duolingo is a place to learn through exercises. Plus, when you do a mouseover, it appears every word what it means and if you have a doubt you can ask (In every exercise there's a "Discuss Sentence", the people of the community will reply you). Besides, this is a friendly and fun page. Viel Spaß!