Is it possible for user to create his own categories for lessons and collect lessons into it depending on level/topic etc.?
Currently it’s not possible but we do have plans to add a feature like this in the very near future. At the moment the closest thing we have is bookmarking a lesson or using the pre-made playlists. Alternatively, you could manually download lessons and group them into playlists on iTunes.
Yay! I am very glad to hear that. I’ve been wanting this feature since I’ve joined a few months ago, so I am so happy to hear that it is in the works!