Ideal way to learn German
What is the ideal way to learn German, do we finish all the levels in skill 1 or do we have to finish level 1 in all the skills ??
I recommend doing each skill completely and then moving on to the next one, then later coming back and practicing the first ones to refresh your memory. That's what I do.
I have been working on six skills at a time, give or take one here and there. I do two skills to level 3 before starting the next two. Once the first two are at 3, I level the next two to 1. First two to 4, next two to 3, next two to 1. Then 5, 4, 3, 1 repeat. I often go back to review finished skills. I find the vocabulary in successive skills seems to reinforce the prior ones. I like to have a couple skills ongoing while working to max a skill or set of skills. I find working to max skills as I go to be the most surefire way to commit new vocab/concepts to my long term memory and not just short term recall. I like to work on small clusters of skills as I work down to provide not only enough variety to not be bored but also enough variety that I am learning how the language fits together, not merely regurgitating set lines without comprehension. That's how I have been working on it. Its whats been working for me. I'm sure if you ask 10 different people, you would get 10 different strategies. Experiment until you find one that works for you. Don't get discouraged while learning the app. Good Luck
I do something similar to erikwingard. The oldest skills are fours and fives, while the newest set goes to a minimum of level two before taking on additional content. I also have focused on some items that are difficult for me like conjunctions, adjectives and adverbs.
On top of Duolingo, I do Tinycards to help with the vocabulary memorization as well as listen to German Music, watch German TV (Netflix has Dark, Generation War and Babylon Berlin which are all very good) and listen to podcasts (Langsam gesprochene Nachrichten is one)
Once I complete the German tree, my plan is to reverse the tree and complete English from German.
I find the best way to study German is to learn vocabulary, word order and grammar in that order. Also, read a lot of German. Above all, go at your own pace until you feel you have a skill down, Language learning is a marathon not a sprint!